meson: drop deprecated EGL platform build options

These two options were deprecated and announced to be removed in 20.3,
so let's drop them now.

Signed-off-by: Eric Engestrom <eric@engestrom.ch>
Acked-by: Emil Velikov <emil.velikov@collabora.com>
Acked-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Cc: 20.3 <mesa-stable>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5844>

meson_options.txt

@@ -23,8 +23,7 @@ option(
   type : 'array',
   value : ['auto'],
   choices : [
-    'auto', 'x11', 'wayland', 'drm', 'surfaceless', 'haiku', 'android',
-    'windows',
+    'auto', 'x11', 'wayland', 'haiku', 'android', 'windows',
   ],
   description : 'window systems to support. If this is set to `auto`, all platforms applicable will be enabled.'
 )