Drop patch version for rust

What does this MR do and why?

All of our larger components don't use patch versions. It's generally very safe to use rolling tag for patch updates. As a minor bonus, the image/tag name is slightly shorter.

• Drops patch version in tags for rust lang

Checklist

• (If applicable) Add patches if required for upgrading Ruby version in https://gitlab.com/gitlab-org/gitlab-build-images/-/tree/master/patches/ruby.