[metacity] compositor: remove obsolete comment

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 395857e7c6787133edf4b0d23fb5d9156fab4075
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Mon Mar 6 17:13:31 2017 +0200

    compositor: remove obsolete comment

 src/compositor/meta-compositor-xrender.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/compositor/meta-compositor-xrender.c b/src/compositor/meta-compositor-xrender.c
index 31de998..c254d35 100644
--- a/src/compositor/meta-compositor-xrender.c
+++ b/src/compositor/meta-compositor-xrender.c
@@ -91,7 +91,7 @@ typedef struct _shadow
 
 typedef struct _MetaCompWindow
 {
-  MetaWindow *window; /* May be NULL if this window isn't managed by Metacity */
+  MetaWindow *window;
   Window id;
   XWindowAttributes attrs;