Replace pg11 with pg14 gitlab images

What does this MR do and why?

This adds a postgres 14 build image variant so we can start running specs against pg 14. Removes the postgres 11 varients since we no longer run postgres 11 builds.

Checklist

• (If applicable) Add patches if required for upgrading Ruby version in https://gitlab.com/gitlab-org/gitlab-build-images/-/tree/master/patches/ruby.