Fix cppcheck warnings in event.c

src/event.c

@@ -790,7 +790,8 @@ int HAMLIB_API rig_set_trn(RIG *rig, int trn)
         {
 #ifdef HAVE_SETITIMER
 
-            retcode = remove_trn_poll_rig(rig);
+            // don't care about the return code here
+            remove_trn_poll_rig(rig);
 
             value.it_value.tv_sec = 0;
             value.it_value.tv_usec = 0;