Add racc dependency because it will be bundled

[skipkayhil]

Motivation / Background

Ruby 3.3.0 is going to start warning for racc not being specififed as a dependency, and Ruby 3.4.0 will raise if it is not specified.

Detail

This commit prevents those issues by adding racc to the Action Pack gemspec, since racc/parser is a runtime dependency of the Journey parser.

Additional information

Ref ruby/ruby@2a56a6c
Ref ruby/ruby#7877

Alternatively, we could vendor racc/parser into Journey's generated parser but that then requires the parser to be regenerated to get any upstream improvements

Checklist

Before submitting the PR make sure the following are checked:

• This Pull Request is related to one change. Changes that are unrelated should be opened in separate PRs.
• Commit message has a detailed description of what changed and why. If this PR fixes a related issue include it in the commit message. Ex: [Fix #issue-number]
• Tests are added or updated if you fix a bug or add a feature.
• CHANGELOG files are updated for the changed libraries if there is a behavior change or additional feature. Minor bug fixes and documentation changes should not be included.

[skipkayhil]

@yahonda what do you think about backporting this to 7-1-stable and 7-0-stable (and also backporting #48907 to 7-0-stable as well) to ensure that 7.0 and 7.1 both show no warnings on 3.3 (and no errors on 3.4)?

[rafaelfranca]

Where are we using racc in Rails?

[rafaelfranca]

Ah, journey.