Skip flaky stream_async_components_for_testing RSpec test (#1941)

## Summary

- Skip flaky `stream_async_components_for_testing` RSpec test that was
replaced by Playwright E2E tests

## Details

This test has been failing on master. Investigation revealed:

1. The test was already replaced by more reliable Playwright E2E tests
in commit b73ff63 "Replace streaming flaky tests with Playwright E2E
tests" (2 weeks ago)
2. The old RSpec tests were kept but are flaky and unreliable for
testing streaming behavior
3. The Playwright tests in `e2e-tests/streaming.spec.ts` provide
comprehensive coverage of the streaming functionality

## Test Coverage

The removed RSpec test is fully covered by Playwright E2E tests which:
- Test incremental rendering of streamed components
- Test early hydration of pages
- Test RSC payload requests
- Provide snapshot-based verification of component states

## Related

- Related commit: b73ff63 "Replace streaming flaky tests with
Playwright E2E tests"
- Similar approach used for "React Router Sixth Page" test which is also
skipped

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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Co-authored-by: Claude <noreply@anthropic.com>

Author: justin808

react_on_rails_pro/spec/dummy/spec/system/integration_spec.rb

@@ -422,7 +422,8 @@ def change_text_expect_dom_selector(dom_selector, expect_no_change: false)
   end
 end
 
-describe "Pages/stream_async_components_for_testing", :js do
+describe "Pages/stream_async_components_for_testing", :js,
+         skip: "Flaky test replaced by Playwright E2E tests in e2e-tests/streaming.spec.ts" do
   it_behaves_like "streamed component tests", "/stream_async_components_for_testing",
                   "#AsyncComponentsTreeForTesting-react-component-0"
 end