Unified storage: Remove unifiedStorageSearchPermissionFiltering feature flag (#109216)

* Unified storage: Remove unifiedStorageSearchPermissionFiltering ff

* unit test

pkg/storage/unified/README.md

@@ -263,8 +263,6 @@ unifiedStorageSearchUI = true
 unifiedStorageSearch = true
 ; (optional) Allows you to sort dashboards by usage insights fields when using enterprise
 ; unifiedStorageSearchSprinkles = true
-; (optional) Will skip search results filter based on user permissions
-; unifiedStorageSearchPermissionFiltering = false
 ```
 
 The dashboard search page has been set up to search unified storage. Additionally, all legacy search calls (e.g. `/api/search`) will go to
@@ -871,7 +869,6 @@ Unified Search requires several feature flags to be enabled depending on the des
 |--------------|---------|-------|--------------|
 | `unifiedStorageSearch` | Core search functionality | Experimental | Search API servers, indexing |
 | `unifiedStorageSearchUI` | Frontend search interface | Experimental | Grafana UI search |
-| `unifiedStorageSearchPermissionFiltering` | User permission filtering | GA | Access control in search results |
 | `unifiedStorageSearchSprinkles` | Usage insights integration | Experimental | Dashboard usage sorting (Enterprise) |
 | `unifiedStorageSearchDualReaderEnabled` | Shadow traffic to unified search | Experimental | Shadow traffic during migration |
 
@@ -887,9 +884,6 @@ unifiedStorageSearch = true
 ; Enable search UI (required for frontend)
 unifiedStorageSearchUI = true
 
-; Enable permission filtering (recommended)
-unifiedStorageSearchPermissionFiltering = true
-
 ; Enable shadow traffic during migration (optional)
 unifiedStorageSearchDualReaderEnabled = true