drop bogus error log 'no MGW fsm'

Looking at a customer's log, these error logs got my attention. There
seems to be no point in logging this at all.

Change-Id: I89dd4fb6913bfb84b6667b159e09968734e2102a

src/osmo-hnbgw/mgw_fsm.c

@@ -782,10 +782,8 @@ int mgw_fsm_handle_rab_ass_resp(struct hnbgw_context_map *map, struct osmo_prim_
  *  \returns 0 on success; negative on error. */
 int mgw_fsm_release(struct hnbgw_context_map *map)
 {
-	if (!map->mgw_fi) {
-		LOGP(DMGW, LOGL_ERROR, "mgw_fsm_release() rua_ctx_id=%d, no MGW fsm -- ignored!\n", map->rua_ctx_id);
+	if (!map->mgw_fi)
 		return -EINVAL;
-	}
 
 	osmo_fsm_inst_dispatch(map->mgw_fi, MGW_EV_RELEASE, NULL);
 	return 0;