Remove unused meta_monitor_get_crtc_mode_for_output

Unused since e52641c4b6 ("cursor-renderer/native: Replace HW cursor
with KMS cursor manager").

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3154>

src/backends/meta-monitor.c

@@ -2166,28 +2166,6 @@ meta_monitor_mode_foreach_output (MetaMonitor          *monitor,
   return TRUE;
 }
 
-MetaMonitorCrtcMode *
-meta_monitor_get_crtc_mode_for_output (MetaMonitor     *monitor,
-                                       MetaMonitorMode *mode,
-                                       MetaOutput      *output)
-{
-  MetaMonitorPrivate *monitor_priv =
-    meta_monitor_get_instance_private (monitor);
-  GList *l;
-  int i;
-
-  for (l = monitor_priv->outputs, i = 0; l; l = l->next, i++)
-    {
-      MetaMonitorCrtcMode *monitor_crtc_mode = &mode->crtc_modes[i];
-
-      if (monitor_crtc_mode->output == output)
-        return monitor_crtc_mode;
-    }
-
-  g_warn_if_reached ();
-  return NULL;
-}
-
 const char *
 meta_monitor_get_display_name (MetaMonitor *monitor)
 {