Update gitlab-mail_room to v0.0.23

What does this MR do and why?

This version is already used by GitLab Omnibus (omnibus-gitlab!6758 (merged)) and Cloud Native GitLab (gitlab-org/build/CNG!1335 (merged)), but we had to avoid updating this dependency in GitLab Rails due to the need to depend on an updated net-imap gem (https://docs.gitlab.com/ee/development/emails.html#rationale). Now that we've updated to Ruby 3.0.5, we can safely bump this version. This version bump is also needed for Ruby 3.1 compatibility.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.