fix(service): Wireguard vpn is on wrong category

[ShadowArcanist]

The service has to be in VPN category instead of VPS

[github-actions]

Hi @ShadowArcanist! 👋

It appears to us that you are either adding a new service or making changes to an existing one.
We kindly ask you to also review and update the Coolify Documentation to include this new service or it's new configuration needs.
This will help ensure that our documentation remains accurate and up-to-date for all users.

Coolify Docs Repository: https://github.com/coollabsio/coolify-docs
How to Contribute a new Service to the Docs: https://coolify.io/docs/get-started/contribute/service#adding-a-new-service-template-to-the-coolify-documentation

[andrasbacsai]

Thank you for the PR!