chore(core): remove client comment feature flag (#13034)

#### PR Dependency Tree


* **PR #13034** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

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

## Summary by CodeRabbit

* **Refactor**
  * Removed the comment feature flag from the application.
* The ability to enable comments now depends solely on server
configuration, not on a feature flag.
* **Chores**
* Cleaned up related feature flag definitions and internal logic for
comment enablement.

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

Co-authored-by: fengmk2 <fengmk2@gmail.com>

packages/frontend/core/src/blocksuite/block-suite-editor/lit-adaper.tsx

@@ -85,10 +85,8 @@ const usePatchSpecs = (mode: DocMode) => {
   const serverService = useService(ServerService);
   const serverConfig = useLiveData(serverService.server.config$);
 
-  const enableComment =
-    useLiveData(featureFlagService.flags.enable_comment.$) &&
-    // comment may not be supported by the server
-    serverConfig.features.includes(ServerFeature.Comment);
+  // comment may not be supported by the server
+  const enableComment = serverConfig.features.includes(ServerFeature.Comment);
 
   const patchedSpecs = useMemo(() => {
     const manager = getViewManager()