fix(retainer): fix test case error

apps/emqx_retainer/src/emqx_retainer_api.erl

@@ -261,4 +261,6 @@ check_bucket_exists(
                 _ ->
                     Cont(Conf)
             end
-    end.
+    end;
+check_bucket_exists(Conf, Cont) ->
+    Cont(Conf).

apps/emqx_retainer/test/emqx_retainer_SUITE.erl

@@ -55,7 +55,6 @@ common_tests() ->
     "    flow_control {\n"
     "        batch_read_number = 0\n"
     "        batch_deliver_number = 0\n"
-    "        batch_deliver_limiter = retainer\n"
     "     }\n"
     "   backend {\n"
     "        type = built_in_database\n"