test(cluster link api): fix flaky test

Ex: https://github.com/emqx/emqx/actions/runs/11107654407/job/30859313603?pr=13888#step:6:400

apps/emqx_cluster_link/test/emqx_cluster_link_api_SUITE.erl

@@ -642,8 +642,6 @@ t_metrics(Config) ->
 
     TargetC1 = emqx_cluster_link_SUITE:start_client(<<"tc1">>, TN1),
     TargetC2 = emqx_cluster_link_SUITE:start_client(<<"tc2">>, TN2),
-    {ok, _, _} = emqtt:subscribe(TargetC1, <<"t/tc1">>),
-    {ok, _, _} = emqtt:subscribe(TargetC2, <<"t/tc2">>),
     {_, {ok, _}} =
         ?wait_async_action(
             begin