reflog gc: a tag that does not point at a commit is not a crime.

Although unusual, tags can point at any object.  Warning only
once is fine, but warning every time about the same tag gets
annoying.

Signed-off-by: Junio C Hamano <junkio@cox.net>

builtin-reflog.c

@@ -263,9 +263,6 @@ static int expire_reflog(const char *ref, const unsigned char *sha1, int unused,
 	}
 
 	cb.ref_commit = lookup_commit_reference_gently(sha1, 1);
-	if (!cb.ref_commit)
-		fprintf(stderr,
-			"warning: ref '%s' does not point at a commit\n", ref);
 	cb.ref = ref;
 	cb.cmd = cmd;
 	for_each_reflog_ent(ref, expire_reflog_ent, &cb);