player: don't try updating subtitles while playback PTS doesn't progress

This code would just keep it busy while e.g. being paused. Even if it's
not paused, it couldn't help with anything since we obviously still lock
display to the externally updated PTS.

player/sub.c

@@ -120,10 +120,10 @@ static bool update_subtitle(struct MPContext *mpctx, double video_pts,
             osd_set_force_video_pts(mpctx->osd, video_pts);
             osd_query_and_reset_want_redraw(mpctx->osd);
             vo_redraw(mpctx->video_out);
-        }
             // Force an arbitrary minimum FPS
             mp_set_timeout(mpctx, 0.1);
         }
+    }
 
     return true;
 }