chore: remove multiple cloud server flag (#12531)

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

- **New Features**
  - The "Add Selfhosted" and "Add Server" options are now displayed whenever the build configuration is native, without relying on feature flags.

- **Refactor**
  - Simplified conditional rendering for server addition buttons by replacing feature flag checks with build configuration checks.

- **Chores**
  - Removed the "Multiple Cloud Servers" feature flag and its related localization strings, streamlining feature management and UI labels.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/frontend/i18n/src/i18n.gen.ts

@@ -5834,14 +5834,6 @@ export function useAFFiNEI18N(): {
       * `Once enabled, users can import and export blocksuite snapshots.`
       */
     ["com.affine.settings.workspace.experimental-features.enable-snapshot-import-export.description"](): string;
-    /**
-      * `Multiple Cloud Servers`
-      */
-    ["com.affine.settings.workspace.experimental-features.enable-multiple-cloud-servers.name"](): string;
-    /**
-      * `Once enabled, users can connect to selfhosted cloud servers.`
-      */
-    ["com.affine.settings.workspace.experimental-features.enable-multiple-cloud-servers.description"](): string;
     /**
       * `Enable Edgeless Editing`
       */