Clean-up ignores that are not ignoring anything (dev/ edition) (#78490)

dev/benchmarks/microbenchmarks/lib/foundation/all_elements_bench.dart

@@ -4,8 +4,7 @@
 
 import 'package:flutter/material.dart';
 import 'package:flutter/scheduler.dart';
-// ignore: implementation_imports
+import 'package:flutter_test/flutter_test.dart' show collectAllElementsFrom;
-import 'package:flutter_test/src/all_elements.dart';
 
 import '../common.dart';
 

dev/integration_tests/flutter_gallery/lib/gallery/icons.dart

@@ -7,7 +7,6 @@ import 'package:flutter/material.dart';
 class GalleryIcons {
   // This class is not meant to be instatiated or extended; this constructor
   // prevents instantiation and extension.
-  // ignore: unused_element
   GalleryIcons._();
 
   static const IconData tooltip = IconData(0xe900, fontFamily: 'GalleryIcons');

dev/tracing_tests/test/default_streams_test.dart

@@ -27,9 +27,6 @@ void main() {
   });
 
   tearDownAll(() async {
-    // TODO(dnfield): Remove ignore once internal repo is up to date
-    // https://github.com/flutter/flutter/issues/74518
-    // ignore: await_only_futures
     await vmService.dispose();
   });
 

dev/tracing_tests/test/image_painting_event_test.dart

@@ -38,9 +38,6 @@ void main() {
   });
 
   tearDownAll(() async {
-    // TODO(dnfield): Remove ignore once internal repo is up to date
-    // https://github.com/flutter/flutter/issues/74518
-    // ignore: await_only_futures
     await vmService.dispose();
   });