Add Ruby 3.3 to CI matrix

[m-nakamura145]

This PR adds Ruby 3.3 to CI matrix. It runs green on local.

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Before submitting the PR make sure the following are checked:

• Feature branch is up-to-date with master (if not - rebase it).
• Squashed related commits together.
• Added tests.
• Updated documentation.
• Added an entry to the CHANGELOG.md if the new code introduces user-observable changes.
• The build (bundle exec rake) passes (be sure to run this locally, since it may produce updated documentation that you will need to commit).

If you have created a new cop:

• Added the new cop to config/default.yml.
• The cop is configured as Enabled: pending in config/default.yml.
• The cop is configured as Enabled: true in .rubocop.yml.
• The cop documents examples of good and bad code.
• The tests assert both that bad code is reported and that good code is not reported.
• Set VersionAdded: "<<next>>" in default/config.yml.

If you have modified an existing cop's configuration options:

• Set VersionChanged: "<<next>>" in config/default.yml.

[pirj]

Thank you!

[pirj]

Wdyt of dropping 2.7 as it’s EOL, and also JRuby? @bquorning @Darhazer @ydah

[bquorning]

We usually only drop support for a Ruby version when RuboCop itself does, and I think we should continue doing it that way.

I’m fine with dropping the CI run for JRuby. I cannot remember one single time where specs failed for JRuby but passed for C Ruby. Of course we would keep supporting JRuby, but just treat problems via bug reports.