[mutter] backend: Remove support for META_DUMMY_MONITORS variable

[Florian Müllner <fmuellner src gnome org>]

commit 43e12dab7b060104d9caab275b208729e8b576cb
Author: Florian Müllner <fmuellner gnome org>
Date:   Thu Apr 23 21:01:43 2020 +0200

    backend: Remove support for META_DUMMY_MONITORS variable
    
    Forcing a dummy monitor manager is unexpected and has been broken
    since commit 315a6f43d.
    
    https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1213

 src/backends/meta-backend.c | 3 ---
 1 file changed, 3 deletions(-)
---
diff --git a/src/backends/meta-backend.c b/src/backends/meta-backend.c
index f75df806b..6c5f61336 100644
--- a/src/backends/meta-backend.c
+++ b/src/backends/meta-backend.c
@@ -809,9 +809,6 @@ static MetaMonitorManager *
 meta_backend_create_monitor_manager (MetaBackend *backend,
                                      GError     **error)
 {
-  if (g_getenv ("META_DUMMY_MONITORS"))
-    return g_object_new (META_TYPE_MONITOR_MANAGER_DUMMY, NULL);
-
   return META_BACKEND_GET_CLASS (backend)->create_monitor_manager (backend,
                                                                    error);
 }