timesync: make manager_is_connected() static

src/timesync/timesyncd-manager.c

@@ -1027,7 +1027,7 @@ clear:
         return r;
 }
 
-bool manager_is_connected(Manager *m) {
+static bool manager_is_connected(Manager *m) {
         assert(m);
 
         /* Return true when the manager is sending a request, resolving a server name, or

src/timesync/timesyncd-manager.h

@@ -131,7 +131,6 @@ void manager_flush_runtime_servers(Manager *m);
 
 int manager_connect(Manager *m);
 void manager_disconnect(Manager *m);
-bool manager_is_connected(Manager *m);
 
 int manager_setup_save_time_event(Manager *m);