Update to Rust 1.73.0
What does this MR do and why?
https://gitlab.com/gitlab-org/ruby/gems/gitlab-glfm-markdown needs at least 1.70.0 - update to latest 1.73.0
Checklist
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(If applicable) Add patches if required for upgrading Ruby version in https://gitlab.com/gitlab-org/gitlab-build-images/-/tree/master/patches/ruby.