Fix a failing test missed in #159108 (#159407)

Missed this test in https://github.com/flutter/flutter/pull/159108

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packages/flutter/test/widgets/custom_painter_test.dart

@@ -355,7 +355,8 @@ void _defineTests() {
     ));
     final Set<SemanticsAction> allActions = SemanticsAction.values.toSet()
       ..remove(SemanticsAction.customAction) // customAction is not user-exposed.
-      ..remove(SemanticsAction.showOnScreen); // showOnScreen is not user-exposed
+      ..remove(SemanticsAction.showOnScreen) // showOnScreen is not user-exposed
+      ..removeWhere((SemanticsAction action) => action.index == 1 << 23);
 
     const int expectedId = 2;
     final TestSemantics expectedSemantics = TestSemantics.root(