shared: make cgit_free_taginfo() public

We will use this function from ui-tag.c in the next patch.

Signed-off-by: John Keeping <john@keeping.me.uk>

shared.c

@@ -203,7 +203,7 @@ static struct refinfo *cgit_mk_refinfo(const char *refname, const struct object_
 	return ref;
 }
 
-static void cgit_free_taginfo(struct taginfo *tag)
+void cgit_free_taginfo(struct taginfo *tag)
 {
 	if (tag->tagger)
 		free(tag->tagger);