Upgrade MailRoom to v0.0.19

What does this MR do?

Upgrade MailRoom gem version to v.0.0.19. This bump fixes the bug that mailroom watcher thread crashes if JWT authentication is used. The bug comes from the lack of dependency loading.

The fix was merged in upstream (https://gitlab.com/gitlab-org/gitlab-mail_room/-/merge_requests/48), synced to our fork (https://gitlab.com/gitlab-org/gitlab-mail_room/-/merge_requests/48), and was released in https://gitlab.com/gitlab-org/gitlab-mail_room/-/merge_requests/49.

Diff: https://my.diffend.io/gems/gitlab-mail_room/0.0.18/0.0.19

Related issues

gitlab-com/gl-infra/scalability#1458 (closed)

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

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