Robert Marshall authored Jun 14, 2021 and DJ Mountney committed Jun 14, 2021

- Removes support for installing repmgr and repmgrd
- Leaves repmgr attributes for detection and deprecation
  warning to administrators when running a reconfigure
- Updates rspec tests to reflect removal of repmgr support

Closes https://gitlab.com/gitlab-org/omnibus-gitlab/-/issues/6174

Changelog: removed