In the following MRs:

1. https://gitlab.com/gitlab-org/gitlab/-/merge_requests/35292
1. https://gitlab.com/gitlab-org/gitlab/-/merge_requests/33176

We broke support support for these previous version by introducing
features that are only available in 6.4+ and 6.2+
https://gitlab.com/gitlab-org/gitlab/-/issues/271218 .

The simplest option here seems to just be to document that it's
unsupported rather than trying to fix these since we're going to remove
support soon anyway for all of `6.x`.