fix override of removeRouteBelow

Author: Conrad598

lib/src/mock_navigator.dart

@@ -319,7 +319,7 @@ class _MockNavigatorState extends NavigatorState {
   }
 
   @override
-  void removeRouteBelow(Route<dynamic> anchorRoute) {
-    return _navigator.removeRouteBelow(anchorRoute);
+  void removeRouteBelow<T extends Object?>(Route<T> anchorRoute, [T? result]) {
+    return _navigator.removeRouteBelow(anchorRoute, result);
   }
 }

test/src/mock_navigator_test.dart

@@ -500,7 +500,9 @@ void main() {
     });
 
     testWidgets('mocks .removeRouteBelow calls', (tester) async {
-      when(() => navigator.removeRouteBelow(any())).thenAnswer((_) {});
+      when(
+        () => navigator.removeRouteBelow<Object?>(any(), any()),
+      ).thenAnswer((_) {});
 
       await tester.pumpTest(
         navigator: navigator,