Reverts "Request focus if SemanticsAction.focus is sent to a focusable widget (#142942)" (#149741)

Reverts: flutter/flutter#142942
Initiated by: zanderso
Reason for reverting: Seems to have affected iOS platform view focus: https://ci.chromium.org/ui/p/flutter/builders/prod/Mac_ios%20native_platform_view_ui_tests_ios/10626/overview
Original PR Author: gspencergoog

Reviewed By: {yjbanov, goderbauer, chunhtai}

This change reverts the following previous change:
## Description

This causes the `Focus` widget to request focus on its focus node if the accessibility system (screen reader) focuses a widget via the `SemanticsAction.focus` action.

## Related Issues
 - https://github.com/flutter/flutter/issues/83809

## Tests
 - Added a test to make sure that focus is requested when `SemanticsAction.focus` is sent by the engine.

dev/integration_tests/flutter_gallery/test/demo/material/chip_demo_test.dart

@@ -20,7 +20,6 @@ void main() {
       isEnabled: true,
       isFocusable: true,
       hasTapAction: true,
-      hasFocusAction: true,
       label: 'Update border shape',
     ));
 
@@ -30,7 +29,6 @@ void main() {
       isEnabled: true,
       isFocusable: true,
       hasTapAction: true,
-      hasFocusAction: true,
       label: 'Reset chips',
     ));