chore(editor): remove feature flag of embed doc with alias (#12620)

<!-- This is an auto-generated comment: release notes by coderabbit.ai -->

## Summary by CodeRabbit

- **New Features**
  - Toolbar actions related to embedding and duplicating documents are now always available without restrictions.

- **Chores**
  - Removed the feature flag controlling embed document alias features for a simpler user experience.

- **Tests**
  - Updated test setup to remove reliance on the deprecated feature flag.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

tests/blocksuite/e2e/embed-synced-doc/edgeless.spec.ts

@@ -142,14 +142,6 @@ test.describe('Embed synced doc in edgeless mode', () => {
         { title: 'Page 1', content: 'hello page 1', inEdgeless: true },
       ]);
 
-      // TODO(@L-Sun): remove this after this feature is released
-      await page.evaluate(() => {
-        const { FeatureFlagService } = window.$blocksuite.services;
-        window.editor.std
-          .get(FeatureFlagService)
-          .setFlag('enable_embed_doc_with_alias', true);
-      });
-
       await switchEditorMode(page);
 
       const edgelessEmbedSyncedBlock = page.locator(