Support Bundler 2.4
What does this MR do and why?
This will help to hopefully make https://gitlab.com/gitlab-org/gitlab-qa/-/jobs/4064061728 pass.
Checklist
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(If applicable) Add patches if required for upgrading Ruby version in https://gitlab.com/gitlab-org/gitlab-build-images/-/tree/master/patches/ruby.
Edited by Rémy Coutable