Mark update-packages as non-experimental (#35465)

diff --git a/packages/flutter_tools/lib/src/commands/update_packages.dart b/packages/flutter_tools/lib/src/commands/update_packages.dart
index 8e98f75..15ac60f 100644
--- a/packages/flutter_tools/lib/src/commands/update_packages.dart
+++ b/packages/flutter_tools/lib/src/commands/update_packages.dart
@@ -78,9 +78,6 @@
   }
 
   @override
-  bool get isExperimental => true;
-
-  @override
   final String name = 'update-packages';
 
   @override