kms: drop window priority below xcb/xdg-shell

The KMS window module shouldn't be loaded when a display server is
running and available from the environment. A user with X11 or Wayland
available can still enforce the kms window module by cleaning the
environment variable from wayland and X11.

Fix #26471

modules/video_output/kms.c

@@ -492,6 +492,6 @@ vlc_module_begin ()
 
     set_description("Linux kernel mode setting window provider")
     set_callback(OpenWindow)
-    set_capability("vout window", 10)
+    set_capability("vout window", 9)
 
 vlc_module_end ()