Bump bundler from 2.6.3 to 2.7.1

[lfdebrux]

What problem does this pull request solve?

Bumps bundler from 2.6.3 to 2.7.1.

When using the latest version of RubyGems with Bundler 2.6.3 a number of redefined constant errors are emitted, so this commit bumps Bundler.

• Release notes
• Changelog
• Commits

Note that this bump drops support for Ruby 3.1.

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• Does it work when run on your machine?
• Is it clear what the code is doing?
• Do the commit messages explain why the changes were made?
• Are there all the unit tests needed?
• Do the end to end tests need updating before these changes will pass?
• Has all relevant documentation been updated?

[github-actions]

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