Remove deprecated KAS `metrics.port` config

What does this MR do?

This MR removes the deprecated gitlab.kas.metrics.port value as per Deprecation of `gitlab.kas.metrics.port` config... (gitlab-org/gitlab#383039 - closed) for %16.0 .

Closes gitlab-org/gitlab#385250 (closed)

Related issues

• Remove `gitlab.kas.metrics.port` configuration ... (gitlab-org/gitlab#385250 - closed)
• Deprecation of `gitlab.kas.metrics.port` config... (gitlab-org/gitlab#383039 - 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
• 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
• Tests added
• Integration tests added to GitLab QA
• Equivalent MR/issue for omnibus-gitlab opened
• Validate potential values for new configuration settings. Formats such as integer 10, duration 10s, URI scheme://user:passwd@host:port may require quotation or other special handling when rendered in a template and written to a configuration file.