chore(unified): remove unifiedStorageSearchSprinkles feature toggle (#116139)

chore: remove unifiedStorageSearchSprinkles feature flag

The feature flag is no longer needed because:
- OSS: usageinsights code doesn't exist in OSS builds
- Enterprise On-Prem: uses local SQL storage when enable_search=true
- Cloud: explicitly configures sprinkles_api_server URL

The sprinkles functionality now works automatically based on:
- enable_search config (enforced true for unified storage mode 5)
- sprinkles_api_server config (empty = local storage, set = remote API)

packages/grafana-data/src/types/featureToggles.gen.ts

@@ -649,10 +649,6 @@ export interface FeatureToggles {
   */
   rolePickerDrawer?: boolean;
   /**
-  * Enable sprinkles on unified storage search
-  */
-  unifiedStorageSearchSprinkles?: boolean;
-  /**
   * Pick the dual write mode from database configs
   */
   managedDualWriter?: boolean;