Remove deprecated CI badge and `Ci::ProjectsController`
Currently we have two CI build badges, one is located in Ci::ProjectsController
and second is a new mechanism with separate controller.
We keep the old one, in order to support existing badges that are fetched using old CI Project id, that is an artifact of GitLab CI -> GitLab merge.
This issue will be used to keep in mind that we should remove a deprecated one at some point in the future (maybe release 9.0 ?).