[DOC] update source policy docs for debian 12

[Sertaç Özercan]

What kind of documentation improvement is needed?

None

What is the change that is needed?

https://project-copacetic.github.io/copacetic/website/faq#can-i-replace-the-package-repositories-in-the-image-with-my-own

Tooling image for Debian-based images are docker.io/library/debian:11-slim ...

tooling image can be 11 or 12 (depends on the target image version)

Are you willing to submit PRs to contribute to documentation?

• Yes, I am willing to implement it.

[Miaha]

Should this change apply to versioned docs as well?

Edit: I've opened a PR. If any changes need to be made, please let me know in the PR.