How to version control Locales / url

I'm using Git and Laravel Forge to deploy my dev and live versions. Working fine, but need to edit my system.yaml everytime I want to deploy because of the 'url' property:

locales:
  nl:
    full: nl_NL
    name: Nederlands
    url: http://website.test/

I do want to include system.yaml into the repo, so I tried setting the url in my .env file (which is excluded from version control). But the {{ env:URL }} doesn't seem to work in the system.yaml file.

Any ideas on how to set this up?

Thx!