[rfw, flutter_markdown] Prepare for removing dart:ui imports. (#5471)

See flutter/flutter#138881
Fixes parts of flutter/flutter#87235

Author: Hixie

packages/flutter_markdown/CHANGELOG.md

@@ -1,6 +1,7 @@
 ## NEXT
 
 * Updates minimum supported SDK version to Flutter 3.10/Dart 3.0.
+* Fixes lint warnings.
 
 ## 0.6.18+2
 

packages/flutter_markdown/lib/src/builder.dart

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// ignore: unnecessary_import (see https://github.com/flutter/flutter/pull/138881)
 import 'dart:ui';
 
 import 'package:flutter/gestures.dart';

packages/rfw/CHANGELOG.md

@@ -1,6 +1,7 @@
 ## NEXT
 
 * Updates minimum supported SDK version to Flutter 3.10/Dart 3.0.
+* Fixes lint warnings.
 
 ## 1.0.15
 

packages/rfw/lib/src/flutter/argument_decoders.dart

@@ -9,6 +9,7 @@
 // This file is hand-formatted.
 
 import 'dart:math' as math show pi;
+// ignore: unnecessary_import (see https://github.com/flutter/flutter/pull/138881)
 import 'dart:ui' show FontFeature; // TODO(ianh): https://github.com/flutter/flutter/issues/87235
 
 import 'package:flutter/material.dart';

packages/rfw/lib/src/flutter/core_widgets.dart

@@ -8,6 +8,7 @@
 
 // This file is hand-formatted.
 
+// ignore: unnecessary_import (see https://github.com/flutter/flutter/pull/138881)
 import 'dart:ui' show FontFeature;
 
 import 'package:flutter/gestures.dart' show DragStartBehavior;