Selfhosted instances of GitLab are not being assigned `gitlab` code host type

[brendan-kellam]

When self-hosting a GitLab instance, we are not recognizing that the code host type is gitlab, resulting in some UI issues. E.g.:

Homepage carousel buttons do not link anywhere:

Codepreview header does not link anywhere:

Guessing this is the same story with a selfhosted GitHub instance, but will create a separate issue when validated.

[gaeljw]

I'm facing this as well (GitLab self hosted)