ref-filter.c: drop return from void function

Sun's C compiler errors out on this pattern:

void foo() { ... }
void bar() { return foo(); }

Signed-off-by: Alejandro R. Sedeño <asedeno@mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

ref-filter.c

@@ -220,7 +220,7 @@ static void objectname_atom_parser(struct used_atom *atom, const char *arg)
 
 static void refname_atom_parser(struct used_atom *atom, const char *arg)
 {
-	return refname_atom_parser_internal(&atom->u.refname, arg, atom->name);
+	refname_atom_parser_internal(&atom->u.refname, arg, atom->name);
 }
 
 static align_type parse_align_position(const char *s)