Dispose ValueNotifier instances in LicensePage state classes (#104589)

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

@@ -426,6 +426,12 @@ class LicensePage extends StatefulWidget {
 class _LicensePageState extends State<LicensePage> {
   final ValueNotifier<int?> selectedId = ValueNotifier<int?>(null);
 
+  @override
+  void dispose() {
+    selectedId.dispose();
+    super.dispose();
+  }
+
   @override
   Widget build(BuildContext context) {
     return _MasterDetailFlow(
@@ -1321,6 +1327,12 @@ class _MasterDetailScaffoldState extends State<_MasterDetailScaffold>
     floatingActionButtonLocation = FloatingActionButtonLocation.endTop;
   }
 
+  @override
+  void dispose() {
+    _detailArguments.dispose();
+    super.dispose();
+  }
+
   @override
   void openDetailPage(Object arguments) {
     SchedulerBinding.instance.addPostFrameCallback((_) => _detailArguments.value = arguments);