Remove TAGS target. It is ages old and has never been updated to match

changes to the source tree. Thus it has to be completely unused.

Originally committed as revision 12610 to svn://svn.ffmpeg.org/ffmpeg/trunk

Makefile

@@ -248,9 +248,6 @@ distclean::
 	$(MAKE) -C libavfilter distclean
 	rm -f .vhookdep version.h config.* *.pc
 
-TAGS:
-	etags *.[ch] libavformat/*.[ch] libavcodec/*.[ch]
-
 # regression tests
 
 fulltest test: codectest libavtest seektest