Update gitlab-mail_room to 0.0.24

What does this MR do?

Remove unused redis-namespace gem (gitlab-org/gitlab!135344 - merged) removed redis-namespace from the GitLab app and starting mail_room failed because we still allow to configure a namespace via config/mail_room.yml:58.

Add redis-namespace gem for mailroom (gitlab-org/gitlab!139259 - merged) readded redis-namespace so we can properly fix the issue with gitlab-mail_room. Now we Specify Redis gems as required dependencies (gitlab-org/ruby/gems/gitlab-mail_room!63 - merged) which was released in gitlab-mail_room 0.0.24.

This MR aims to pull in these changes and fix the installed dependencies to the current versions.

Related issues

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion

Required

• Merge Request Title, and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com
• When ready for review, MR is labeled "~workflow::ready for review" per the Distribution MR workflow

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated
• Integration tests added to GitLab QA
• The impact any change in container size has should be evaluated
• New dependencies are managed with dependencies.io