Add ruby-3.4.0-rc1

[ruby-builder-bot]

Automated PR from ruby/ruby-builder

[eregon]

@hsbt If you'd like, you can add new Ruby releases to setup-ruby.
How it works:

• Make sure the version is added to ruby-build master first.
• Run this workflow or wait it runs (once a day). It will create a PR such as this one.
• Merge the PR
• Run this workflow to create a release of setup-ruby and automatically update the v1 branch.

I'll do it for this one, feel free to do it for the next RC/release/etc.