Remove unnecessary pub upgrade from update-version command (#6877)

* Remove unnecessary pub upgrade from update-version command

* remove unused import

tool/lib/commands/update_version.dart

diff --git a/tool/lib/commands/update_version.dart b/tool/lib/commands/update_version.dart
index 341011e..d3c2540 100644
--- a/tool/lib/commands/update_version.dart
+++ b/tool/lib/commands/update_version.dart
@@ -5,7 +5,6 @@
 import 'dart:io';
 
 import 'package:args/command_runner.dart';
-import 'package:devtools_tool/devtools_command_runner.dart';
 import '../utils.dart';
 
 // This script must be executed from the top level devtools/ directory.
@@ -54,12 +53,6 @@
     File(pathFromRepoRoot('packages/devtools_app/lib/devtools.dart')),
     newVersion,
   );
-
-  await DevToolsCommandRunner().run([
-    'pub-get',
-    '--upgrade',
-    '--only-main',
-  ]);
 }
 
 Future<void> resetReleaseNotes({