ref-filter: remove ref_format_clear()

Now that ref_format_clear() no longer releases any memory we don't need
it anymore.  Remove it and its counterpart, ref_format_init().

Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/branch.c

@@ -884,7 +884,6 @@ int cmd_branch(int argc,
 		string_list_clear(&output, 0);
 		ref_sorting_release(sorting);
 		ref_filter_clear(&filter);
-		ref_format_clear(&format);
 
 		ret = 0;
 		goto out;