Deprecate and remove service template metrics
Description
As part of the removal of the service templates #325659 (closed), we have to deprecate and finally remove the following line https://gitlab.com/gitlab-org/gitlab/-/blob/d6ab412b1964eb60e5e84c9a046397ea610ae250/lib/gitlab/usage_data.rb#L411.
In order to do that, we have to follow the process to deprecate and remove an usage ping metric:
Edited by Arturo Herrero