Fix one notDisposed leak and mark another. (#133595)

packages/flutter/lib/src/material/bottom_sheet.dart

@@ -1005,6 +1005,12 @@ class ModalBottomSheetRoute<T> extends PopupRoute<T> {
 
   final ValueNotifier<EdgeInsets> _clipDetailsNotifier = ValueNotifier<EdgeInsets>(EdgeInsets.zero);
 
+  @override
+  void dispose() {
+    _clipDetailsNotifier.dispose();
+    super.dispose();
+  }
+
   /// Updates the details regarding how the [SemanticsNode.rect] (focus) of
   /// the barrier for this [ModalBottomSheetRoute] should be clipped.
   ///

packages/flutter/test/material/bottom_sheet_test.dart

@@ -7,6 +7,7 @@ import 'dart:ui';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
+import 'package:leak_tracker_flutter_testing/leak_tracker_flutter_testing.dart';
 
 import '../widgets/semantics_tester.dart';
 
@@ -1672,7 +1673,8 @@ void main() {
   });
 
   group('Modal BottomSheet avoids overlapping display features', () {
-    testWidgets('positioning using anchorPoint', (WidgetTester tester) async {
+    testWidgetsWithLeakTracking('positioning using anchorPoint',
+    (WidgetTester tester) async {
       await tester.pumpWidget(
         MaterialApp(
           builder: (BuildContext context, Widget? child) {
@@ -1708,7 +1710,12 @@ void main() {
       // Should take the right side of the screen
       expect(tester.getTopLeft(find.byType(Placeholder)).dx, 410);
       expect(tester.getBottomRight(find.byType(Placeholder)).dx, 800);
-    });
+    },
+    leakTrackingTestConfig: const LeakTrackingTestConfig(
+      // TODO(polina-c): remove after fix
+      // https://github.com/flutter/flutter/issues/133594
+      notDisposedAllowList: <String, int?> {'ValueNotifier<EdgeInsets>': 1}
+    ));
 
     testWidgets('positioning using Directionality', (WidgetTester tester) async {
       await tester.pumpWidget(