Temporarily change tests to accommodate new SemanticsAction value (#159108)

This is for fixing a test failure in an engine PR that introduces a new
`SemanticsAction`: https://github.com/flutter/engine/pull/56606/files

The test will be updated in the future to remove the index-based
predicate.

failure:
https://logs.chromium.org/logs/flutter/buildbucket/cr-buildbucket/8730901009848520305/+/u/run_test.dart_for_web_tests_shard_and_subshard_1/stdout

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packages/flutter/test/widgets/semantics_test.dart

@@ -524,7 +524,8 @@ void main() {
       ..remove(SemanticsAction.moveCursorForwardByWord)
       ..remove(SemanticsAction.moveCursorBackwardByWord)
       ..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 = 1;
     final TestSemantics expectedSemantics = TestSemantics.root(