remove obsolate comment

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@17257 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavcodec/mpegvideo_xvmc.c

@@ -29,10 +29,6 @@
 #undef NDEBUG
 #include <assert.h>
 
-//X11 includes are in libavcodec/xvmc.h
-//by replacing it with non-X one
-//XvMC emulation could be performed
-
 #include "xvmc.h"
 
 //set s->block