Mention `dart pub` (#2823)

diff --git a/lib/src/command/outdated.dart b/lib/src/command/outdated.dart
index 98248d1..b2e7aa6 100644
--- a/lib/src/command/outdated.dart
+++ b/lib/src/command/outdated.dart
@@ -545,12 +545,12 @@
       if (upgradable == 1) {
         log.message('\n1 upgradable dependency is locked (in pubspec.lock) to '
             'an older version.\n'
-            'To update it, use `pub upgrade`.');
+            'To update it, use `dart pub upgrade`.');
       } else {
         log.message(
             '\n$upgradable upgradable dependencies are locked (in pubspec.lock) '
             'to older versions.\n'
-            'To update these dependencies, use `pub upgrade`.');
+            'To update these dependencies, use `dart pub upgrade`.');
       }
     }
   } else {
diff --git a/test/outdated/goldens/circular_dependencies.txt b/test/outdated/goldens/circular_dependencies.txt
index 7f7be45..27b6202 100644
--- a/test/outdated/goldens/circular_dependencies.txt
+++ b/test/outdated/goldens/circular_dependencies.txt
@@ -29,7 +29,7 @@
 foo           *1.2.3   1.3.0       1.3.0       1.3.0   
 
 1 upgradable dependency is locked (in pubspec.lock) to an older version.
-To update it, use `pub upgrade`.
+To update it, use `dart pub upgrade`.
 
 $ pub outdated --no-color --no-transitive
 Showing outdated packages.
@@ -41,7 +41,7 @@
 foo           *1.2.3   1.3.0       1.3.0       1.3.0   
 
 1 upgradable dependency is locked (in pubspec.lock) to an older version.
-To update it, use `pub upgrade`.
+To update it, use `dart pub upgrade`.
 
 $ pub outdated --no-color --up-to-date
 Showing outdated packages.
@@ -53,7 +53,7 @@
 foo           *1.2.3   1.3.0       1.3.0       1.3.0   
 
 1 upgradable dependency is locked (in pubspec.lock) to an older version.
-To update it, use `pub upgrade`.
+To update it, use `dart pub upgrade`.
 
 $ pub outdated --no-color --prereleases
 Showing outdated packages.
@@ -65,7 +65,7 @@
 foo           *1.2.3   1.3.0       1.3.0       1.3.0   
 
 1 upgradable dependency is locked (in pubspec.lock) to an older version.
-To update it, use `pub upgrade`.
+To update it, use `dart pub upgrade`.
 
 $ pub outdated --no-color --no-dev-dependencies
 Showing outdated packages.
@@ -77,7 +77,7 @@
 foo           *1.2.3   1.3.0       1.3.0       1.3.0   
 
 1 upgradable dependency is locked (in pubspec.lock) to an older version.
-To update it, use `pub upgrade`.
+To update it, use `dart pub upgrade`.
 
 $ pub outdated --no-color --no-dependency-overrides
 Showing outdated packages.
@@ -89,7 +89,7 @@
 foo           *1.2.3   1.3.0       1.3.0       1.3.0   
 
 1 upgradable dependency is locked (in pubspec.lock) to an older version.
-To update it, use `pub upgrade`.
+To update it, use `dart pub upgrade`.
 
 $ pub outdated --no-color --mode=null-safety
 Showing dependencies that are currently not opted in to null-safety.
@@ -102,7 +102,7 @@
 foo           ✗1.2.3   ✗1.3.0      ✗1.3.0      ✗1.3.0  
 
 1 upgradable dependency is locked (in pubspec.lock) to an older version.
-To update it, use `pub upgrade`.
+To update it, use `dart pub upgrade`.
 
 $ pub outdated --no-color --mode=null-safety --transitive
 Showing dependencies that are currently not opted in to null-safety.
@@ -115,7 +115,7 @@
 foo           ✗1.2.3   ✗1.3.0      ✗1.3.0      ✗1.3.0  
 
 1 upgradable dependency is locked (in pubspec.lock) to an older version.
-To update it, use `pub upgrade`.
+To update it, use `dart pub upgrade`.
 
 $ pub outdated --no-color --mode=null-safety --no-prereleases
 Showing dependencies that are currently not opted in to null-safety.
@@ -128,7 +128,7 @@
 foo           ✗1.2.3   ✗1.3.0      ✗1.3.0      ✗1.3.0  
 
 1 upgradable dependency is locked (in pubspec.lock) to an older version.
-To update it, use `pub upgrade`.
+To update it, use `dart pub upgrade`.
 
 $ pub outdated --json --mode=null-safety
 {
diff --git a/test/outdated/goldens/dependency_overrides.txt b/test/outdated/goldens/dependency_overrides.txt
index 16acdc9..159fc50 100644
--- a/test/outdated/goldens/dependency_overrides.txt
+++ b/test/outdated/goldens/dependency_overrides.txt
@@ -135,7 +135,7 @@
 foo           *1.0.1 (overridden)  *1.0.0      *1.0.0      2.0.0   
 
 3 upgradable dependencies are locked (in pubspec.lock) to older versions.
-To update these dependencies, use `pub upgrade`.
+To update these dependencies, use `dart pub upgrade`.
 
 1 dependency is constrained to a version that is older than a resolvable version.
 To update it, edit pubspec.yaml.
diff --git a/test/outdated/goldens/newer_versions.txt b/test/outdated/goldens/newer_versions.txt
index 2f36e62..f44c202 100644
--- a/test/outdated/goldens/newer_versions.txt
+++ b/test/outdated/goldens/newer_versions.txt
@@ -105,7 +105,7 @@
 transitive3   -        -           1.0.0       1.0.0   
 
 3 upgradable dependencies are locked (in pubspec.lock) to older versions.
-To update these dependencies, use `pub upgrade`.
+To update these dependencies, use `dart pub upgrade`.
 
 3  dependencies are constrained to versions that are older than a resolvable version.
 To update these dependencies, edit pubspec.yaml.
@@ -123,7 +123,7 @@
 builder       *1.2.3   *1.3.0      2.0.0       2.0.0   
 
 2 upgradable dependencies are locked (in pubspec.lock) to older versions.
-To update these dependencies, use `pub upgrade`.
+To update these dependencies, use `dart pub upgrade`.
 
 2  dependencies are constrained to versions that are older than a resolvable version.
 To update these dependencies, edit pubspec.yaml.
@@ -151,7 +151,7 @@
 transitive3    -        -           1.0.0       1.0.0   
 
 3 upgradable dependencies are locked (in pubspec.lock) to older versions.
-To update these dependencies, use `pub upgrade`.
+To update these dependencies, use `dart pub upgrade`.
 
 3  dependencies are constrained to versions that are older than a resolvable version.
 To update these dependencies, edit pubspec.yaml.
@@ -177,7 +177,7 @@
 transitive3   -        -           1.0.0       1.0.0        
 
 3 upgradable dependencies are locked (in pubspec.lock) to older versions.
-To update these dependencies, use `pub upgrade`.
+To update these dependencies, use `dart pub upgrade`.
 
 3  dependencies are constrained to versions that are older than a resolvable version.
 To update these dependencies, edit pubspec.yaml.
@@ -195,7 +195,7 @@
 transitive    *1.2.3   2.0.0       2.0.0       2.0.0   
 
 2 upgradable dependencies are locked (in pubspec.lock) to older versions.
-To update these dependencies, use `pub upgrade`.
+To update these dependencies, use `dart pub upgrade`.
 
 1 dependency is constrained to a version that is older than a resolvable version.
 To update it, edit pubspec.yaml.
@@ -221,7 +221,7 @@
 transitive3   -        -           1.0.0       1.0.0   
 
 3 upgradable dependencies are locked (in pubspec.lock) to older versions.
-To update these dependencies, use `pub upgrade`.
+To update these dependencies, use `dart pub upgrade`.
 
 3  dependencies are constrained to versions that are older than a resolvable version.
 To update these dependencies, edit pubspec.yaml.
@@ -242,7 +242,7 @@
 builder        ✗1.2.3   ✗1.3.0      ✗2.0.0      ✗3.0.0-alpha  
 
 2 upgradable dependencies are locked (in pubspec.lock) to older versions.
-To update these dependencies, use `pub upgrade`.
+To update these dependencies, use `dart pub upgrade`.
 
 2  dependencies are constrained to versions that are older than a resolvable version.
 To update these dependencies, edit pubspec.yaml.
@@ -271,7 +271,7 @@
 transitive3    -        -           ✗1.0.0      ✗1.0.0        
 
 3 upgradable dependencies are locked (in pubspec.lock) to older versions.
-To update these dependencies, use `pub upgrade`.
+To update these dependencies, use `dart pub upgrade`.
 
 3  dependencies are constrained to versions that are older than a resolvable version.
 To update these dependencies, edit pubspec.yaml.
@@ -292,7 +292,7 @@
 builder        ✗1.2.3   ✗1.3.0      ✗2.0.0      ✗2.0.0  
 
 2 upgradable dependencies are locked (in pubspec.lock) to older versions.
-To update these dependencies, use `pub upgrade`.
+To update these dependencies, use `dart pub upgrade`.
 
 2  dependencies are constrained to versions that are older than a resolvable version.
 To update these dependencies, edit pubspec.yaml.