Fix CI

[olivier-thatch]

CI is broken. This PR fixes it.

There were 2 issues:

• jruby 9.4.6 is no longer available via the setup-ruby action. I changed the version to jruby-9.4 to install the latest 9.4.x version
• this issue with Rails 6.1. Fixed by adding require 'logger' in a couple places.

I only made the minimum changes to get CI to pass again, but I would recommend making the following changes as well:

• drop Ruby 2.7 and 3.0 from the matrix, and add Ruby 3.4
• drop Rails 6.1 from the matrix and add Rails 8.0
• replace jruby-9.4 with just jruby to run the latest stable JRuby

@dblock Let me know if you want me to make any of the above changes, or any other changes.

[grape-bot]

	1 Warning
⚠️	Unless you're refactoring existing code or improving documentation, please update CHANGELOG.md.

Here's an example of a CHANGELOG.md entry:

* [#131](https://github.com/ruby-grape/grape-swagger-rails/pull/131): Fix ci - [@olivier-thatch](https://github.com/olivier-thatch).

Generated by 🚫 Danger

[dblock]

Thanks! Generally we drop compatibility with old versions only if it really simplifies something, but feel free to do it! Yes for Ruby 3.4, etc. Either way, I'll merge this in any 🟢 state (needs a rubocop fix/run), appreciate you picking it up!

[olivier-thatch]

Rubocop issue is fixed. I'll do the matrix update in a separate PR.