fix(tests): improve reliability of pre-filter validation test

Replace `waitFor` with `getByText` pattern with `findByText` which automatically
waits for the element to appear. This follows React Testing Library best practices
and eliminates flaky test failures caused by timing issues with fake/real timers.

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

Co-Authored-By: Claude <noreply@anthropic.com>

Author: eschutho

superset-frontend/src/dashboard/components/nativeFilters/FiltersConfigModal/FiltersConfigModal.test.tsx

@@ -346,9 +346,9 @@ test('validates the pre-filter value', async () => {
   jest.runOnlyPendingTimers();
   jest.useRealTimers();
 
-  await waitFor(() => {
-    expect(screen.getByText(PRE_FILTER_REQUIRED_REGEX)).toBeInTheDocument();
-  });
+  expect(
+    await screen.findByText(PRE_FILTER_REQUIRED_REGEX),
+  ).toBeInTheDocument();
 }, 50000); // Slow-running test, increase timeout to 50 seconds.
 
 // eslint-disable-next-line jest/no-disabled-tests