CLEANUP: acl: remove unused references to ACL_USE_*

Now that acl->requires is not used anymore, we can remove all references
to it as well as all ACL_USE_* flags.
diff --git a/src/listener.c b/src/listener.c
index 862e1e4..32b5bad 100644
--- a/src/listener.c
+++ b/src/listener.c
@@ -653,8 +653,8 @@
  * Please take care of keeping this list alphabetically sorted.
  */
 static struct acl_kw_list acl_kws = {{ },{
-	{ "dst_conn",  NULL, acl_parse_int, acl_match_int, ACL_USE_NOTHING },
-	{ "so_id",     NULL, acl_parse_int, acl_match_int, ACL_USE_NOTHING },
+	{ "dst_conn",  NULL, acl_parse_int, acl_match_int },
+	{ "so_id",     NULL, acl_parse_int, acl_match_int },
 	{ /* END */ },
 }};