Prepare for 0.21.0 publish (#1757)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index e656975..21bcdd4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,4 +1,4 @@
-## 0.21.0-dev.0
+## 0.21.0
 * Expand categories to all top level items as well as libraries.  (#1681, #1353)
 * The categoryOrder option in dartdoc_options.yaml and the command line
   is replaced with a more generic "categories" option.  See README.md.
diff --git a/lib/src/version.dart b/lib/src/version.dart
index 43e6540..8978505 100644
--- a/lib/src/version.dart
+++ b/lib/src/version.dart
@@ -1,2 +1,2 @@
 // Generated code. Do not modify.
-const packageVersion = '0.21.0-dev.0';
+const packageVersion = '0.21.0';
diff --git a/pubspec.yaml b/pubspec.yaml
index 1a279a7..4de7541 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,6 +1,6 @@
 name: dartdoc
 # Also update the `version` field in lib/dartdoc.dart.
-version: 0.21.0-dev.0
+version: 0.21.0
 author: Dart Team <misc@dartlang.org>
 description: A documentation generator for Dart.
 homepage: https://github.com/dart-lang/dartdoc
diff --git a/testing/test_package_docs/__404error.html b/testing/test_package_docs/__404error.html
index 938d312..229932b 100644
--- a/testing/test_package_docs/__404error.html
+++ b/testing/test_package_docs/__404error.html
@@ -4,7 +4,7 @@
   <meta charset="utf-8">
   <meta http-equiv="X-UA-Compatible" content="IE=edge">
   <meta name="viewport" content="width=device-width, initial-scale=1">
-  <meta name="generator" content="made with love by dartdoc 0.21.0-dev.0">
+  <meta name="generator" content="made with love by dartdoc 0.21.0">
   <meta name="description" content="test_package API docs, for the Dart programming language.">
   <title>test_package - Dart API docs</title>
 
diff --git a/testing/test_package_docs/index.html b/testing/test_package_docs/index.html
index e41af20..3e09a7e 100644
--- a/testing/test_package_docs/index.html
+++ b/testing/test_package_docs/index.html
@@ -4,7 +4,7 @@
   <meta charset="utf-8">
   <meta http-equiv="X-UA-Compatible" content="IE=edge">
   <meta name="viewport" content="width=device-width, initial-scale=1">
-  <meta name="generator" content="made with love by dartdoc 0.21.0-dev.0">
+  <meta name="generator" content="made with love by dartdoc 0.21.0">
   <meta name="description" content="test_package API docs, for the Dart programming language.">
   <title>test_package - Dart API docs</title>
 
diff --git a/testing/test_package_docs_dev/__404error.html b/testing/test_package_docs_dev/__404error.html
index 938d312..229932b 100644
--- a/testing/test_package_docs_dev/__404error.html
+++ b/testing/test_package_docs_dev/__404error.html
@@ -4,7 +4,7 @@
   <meta charset="utf-8">
   <meta http-equiv="X-UA-Compatible" content="IE=edge">
   <meta name="viewport" content="width=device-width, initial-scale=1">
-  <meta name="generator" content="made with love by dartdoc 0.21.0-dev.0">
+  <meta name="generator" content="made with love by dartdoc 0.21.0">
   <meta name="description" content="test_package API docs, for the Dart programming language.">
   <title>test_package - Dart API docs</title>
 
diff --git a/testing/test_package_docs_dev/index.html b/testing/test_package_docs_dev/index.html
index e41af20..3e09a7e 100644
--- a/testing/test_package_docs_dev/index.html
+++ b/testing/test_package_docs_dev/index.html
@@ -4,7 +4,7 @@
   <meta charset="utf-8">
   <meta http-equiv="X-UA-Compatible" content="IE=edge">
   <meta name="viewport" content="width=device-width, initial-scale=1">
-  <meta name="generator" content="made with love by dartdoc 0.21.0-dev.0">
+  <meta name="generator" content="made with love by dartdoc 0.21.0">
   <meta name="description" content="test_package API docs, for the Dart programming language.">
   <title>test_package - Dart API docs</title>