contrib: ffmpeg: Remove SNAPURL

It's been unused since b49f27fc

contrib/src/ffmpeg/rules.mak

@@ -6,13 +6,11 @@
 
 ifndef USE_LIBAV
 FFMPEG_HASH=d0e740b8fb30f02914594d00eb311a32442a63f8
-FFMPEG_SNAPURL := http://git.videolan.org/?p=ffmpeg.git;a=snapshot;h=$(FFMPEG_HASH);sf=tgz
 FFMPEG_GITURL := http://git.videolan.org/git/ffmpeg.git
 FFMPEG_LAVC_MIN := 57.37.100
 USE_FFMPEG := 1
 else
 FFMPEG_HASH=35ed7f93dbc72d733e454ae464b1324f38af62a0
-FFMPEG_SNAPURL := http://git.libav.org/?p=libav.git;a=snapshot;h=$(FFMPEG_HASH);sf=tgz
 FFMPEG_GITURL := git://git.libav.org/libav.git
 FFMPEG_LAVC_MIN := 57.16.0
 endif