fix tenant connection map ref count leak

src/sql/session/ob_user_resource_mgr.cpp

@@ -164,6 +164,7 @@ void ObConnectResourceMgr::release_tenant_conn_resource(const uint64_t tenant_id
     } else {
       tenant_res->cur_connections_--;
     }
+    tenant_res_map_.revert(tenant_res);
   }
 }