fix(queue): enable queues for EE

apps/emqx/src/emqx_persistent_session_ds/shared_subs_agent.hrl

@@ -18,10 +18,7 @@
 %% clause of -ifdef(TEST).
 -else.
 
-%% Till full implementation we need to dispach to the null agent.
-%% It will report "not implemented" error for attempts to use shared subscriptions.
--define(shared_subs_agent, emqx_persistent_session_ds_shared_subs_null_agent).
-% -define(shared_subs_agent, emqx_ds_shared_sub_agent).
+-define(shared_subs_agent, emqx_ds_shared_sub_agent).
 
 %% end of -ifdef(TEST).
 -endif.