docs(tests): explain why antd mock is used for Grid.useBreakpoint

Added comment explaining that we mock 'antd' directly rather than
'@superset-ui/core/components' because the latter causes circular
dependency issues with ActionButton during jest.requireActual
evaluation. Since Grid is re-exported from antd, mocking antd works.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: rusackas

superset-frontend/src/features/home/Menu.test.tsx

@@ -25,6 +25,9 @@ import { Menu } from './Menu';
 import * as getBootstrapData from 'src/utils/getBootstrapData';
 
 // Mock useBreakpoint to return desktop breakpoints (prevents mobile menu rendering)
+// Note: We mock 'antd' directly rather than '@superset-ui/core/components' because
+// mocking the latter causes circular dependency issues with ActionButton during
+// jest.requireActual evaluation. Since Grid is re-exported from antd, this works.
 jest.mock('antd', () => ({
   ...jest.requireActual('antd'),
   Grid: {