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>

blocksuite/affine/shared/src/services/feature-flag-service.ts

@@ -21,7 +21,6 @@ export interface BlockSuiteFlags {
   enable_table_virtual_scroll: boolean;
   enable_turbo_renderer: boolean;
   enable_dom_renderer: boolean;
-  enable_comment: boolean;
 }
 
 export class FeatureFlagService extends StoreExtension {
@@ -47,7 +46,6 @@ export class FeatureFlagService extends StoreExtension {
     enable_table_virtual_scroll: false,
     enable_turbo_renderer: false,
     enable_dom_renderer: false,
-    enable_comment: false,
   });
 
   setFlag(key: keyof BlockSuiteFlags, value: boolean) {