The repository languages feature got introduced through:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/19480. This MR
included feature flags to guard against performance regressions, which
allowed GitLab to test it on gitlab.com before the customers would be
exposed.

.com worked out fine, as shown by our internal monitoring tools, which
prompts feature gate removal.

Given the docs weren't present yet, these were added too.