docs: Add missing await in Indexed DB persister example (#6012)

Add missing await in Indexed DB persister example

Author: cjsewell

docs/react/plugins/persistQueryClient.md

@@ -264,7 +264,7 @@ import { PersistedClient, Persister } from "@tanstack/react-query-persist-client
 export function createIDBPersister(idbValidKey: IDBValidKey = "reactQuery") {
   return {
     persistClient: async (client: PersistedClient) => {
-      set(idbValidKey, client);
+      await set(idbValidKey, client);
     },
     restoreClient: async () => {
       return await get<PersistedClient>(idbValidKey);