Remove Swift 6.0 from CI matrix, keeping only Swift 6.1

[meatball133]

Swift 6 ci is now also broken (Ubuntu was broken and removed). I would suppose that this is caused by the underlying macos image changed which caused it to fail. For now the easiest fix is just removing the ci.

[github-actions]

Hello 👋 Thanks for your PR.

This repo does not currently have dedicated maintainers. Our cross-track maintainers team will attempt to review and merge your PR, but it will likely take longer for your PR to be reviewed.

If you enjoy contributing to Exercism and have a track-record of doing so successfully, you might like to become an Exercism maintainer for this track.

Please feel free to ask any questions, or chat to us about anything to do with this PR or the reviewing process on the Exercism forum.

(cc @exercism/cross-track-maintainers)

[Sencudra]

Looks okay for me. Initially, what was the idea to add both 6.0 and 6.1?

[meatball133]

Looks okay for me. Initially, what was the idea to add both 6.0 and 6.1?

Generally, it is a good idea to support multiple versions, so people aren't forced to use the latest versions. For example Linux distrubtions doesnt always have the latest version of a package, which makes it annyoing to install sometimes.