Do you
want to or
need to update?
If you do not need to update because of a problem or missing feature, don't. Just enjoy cops as is.
If you need to update or just really want to you have two options:
1 - use a docker container on synology. (I never tried it. My synology is to old.)
https://github.com/seblucas/cops/releases
2 - copy a released version of cops into your ./web/cops directory of your synology and copy your old config_local.php file into it. Maybe some fiddling with the settings and it will work (did for me).
https://github.com/seblucas/cops/releases