Remove `package:shelf` version pin (#105261)

packages/flutter_tools/lib/src/commands/update_packages.dart

@@ -31,10 +31,6 @@ const Map<String, String> kManuallyPinnedDependencies = <String, String>{
   'archive': '3.1.11', // Breaking changes in 3.2.0, see https://github.com/flutter/flutter/issues/98536
   'flutter_gallery_assets': '1.0.2', // Tests depend on the exact version.
   'flutter_template_images': '4.1.0', // Must always exactly match flutter_tools template.
-  // "shelf" is pinned to avoid the performance regression from a reverted
-  // feature from https://github.com/dart-lang/shelf/issues/189 . This can be
-  // removed when a new major version of shelf is published.
-  'shelf': '1.1.4',
   'video_player': '2.2.11',
   // Could potentially break color scheme tests on upgrade,
   // so pin and manually update as needed.