persistent_cache_index_manager.ts: added @internal tag to deleteAllPersistentCacheIndexes()

Author: dconeybe

packages/firestore/src/api/persistent_cache_index_manager.ts

@@ -107,6 +107,9 @@ export function disablePersistentCacheIndexAutoCreation(
  *
  * Please note this function will also deletes indexes generated by
  * `setIndexConfiguration()`, which is deprecated.
+ *
+ * TODO(CSI) Remove @internal to make the API publicly available.
+ * @internal
  */
 export function deleteAllPersistentCacheIndexes(
   indexManager: PersistentCacheIndexManager