fix draggable_scrollable_sheet_test.dart (#90204)

packages/flutter/test/widgets/draggable_scrollable_sheet_test.dart

@@ -113,10 +113,7 @@ void main() {
     expect(tester.takeException(), isAssertionError);
   });
 
-  for (final TargetPlatform platform in TargetPlatform.values) {
-    group('$platform Scroll Physics', () {
-      debugDefaultTargetPlatformOverride = platform;
-
+  group('Scroll Physics', () {
     testWidgets('Can be dragged up without covering its container', (WidgetTester tester) async {
       int taps = 0;
       await tester.pumpWidget(_boilerplate(() => taps++));
@@ -326,8 +323,6 @@ void main() {
       expect(find.text('Item 31'), findsNothing);
       expect(find.text('Item 70'), findsNothing);
     }, variant: TargetPlatformVariant.all());
-
-      debugDefaultTargetPlatformOverride = null;
   });
 
   testWidgets('Does not snap away from initial child on build', (WidgetTester tester) async {
@@ -575,5 +570,4 @@ void main() {
 
     expect(tester.takeException(), isNull);
   });
-  }
 }