Bump bundler from 2.6.3 to 2.7.1

Bumps [bundler](https://bundler.io/) 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](https://github.com/rubygems/rubygems/releases/tag/bundler-v2.7.1)
- [Changelog](https://github.com/rubygems/rubygems/blob/bundler-v2.7.1/bundler/CHANGELOG.md)
- [Commits](rubygems/[email protected])

Note that this bump drops support for Ruby 3.1.

Author: lfdebrux

Gemfile.lock

@@ -152,4 +152,4 @@ RUBY VERSION
    ruby 3.4.1p0
 
 BUNDLED WITH
-   2.6.3
+   2.7.1