[flutter_tools] Restore base/platform.dart (#56410)

packages/flutter_tools/lib/src/base/user_messages.dart

diff --git a/packages/flutter_tools/lib/src/base/user_messages.dart b/packages/flutter_tools/lib/src/base/user_messages.dart
index 8d9652a..a1a3163 100644
--- a/packages/flutter_tools/lib/src/base/user_messages.dart
+++ b/packages/flutter_tools/lib/src/base/user_messages.dart
@@ -2,9 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'package:platform/platform.dart';
-
 import 'context.dart';
+import 'platform.dart';
 
 UserMessages get userMessages => context.get<UserMessages>();