What does this MR do?

Adds postgres 14 to the builds in order to test our support of it.

Related issues

• Relates to:
  • Research spike: Adding support for PG14 (#7396 - closed)
  • Update the default postgresql to PG 13 or 14 (gitlab-org/charts/gitlab#4118 - closed)
  • Remove PostgreSQL 12 from Omnibus (#7395 - closed)
  • Add postgres removal warning for PG12 in GitLab... (#7394 - closed)
• Closes #7702 (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
• Pipeline is green on dev.gitlab.org if the change is touching anything besides documentation or internal cookbooks
• trigger-package has a green pipeline running against latest commit

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 the GitLab Chart opened