Date picker dialog state should dispose members. (flutter#134804)

Author: polina-c

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

@@ -416,6 +416,14 @@ class _DatePickerDialogState extends State<DatePickerDialog> with RestorationMix
   late final _RestorableDatePickerEntryMode _entryMode = _RestorableDatePickerEntryMode(widget.initialEntryMode);
   final _RestorableAutovalidateMode _autovalidateMode = _RestorableAutovalidateMode(AutovalidateMode.disabled);
 
+  @override
+  void dispose() {
+    _selectedDate.dispose();
+    _entryMode.dispose();
+    _autovalidateMode.dispose();
+    super.dispose();
+  }
+
   @override
   String? get restorationId => widget.restorationId;