Add note in docs about needing gitlab ee for approval requirements

[jukie]

what

Adds docs notice for Gitlab Premium requirement to use approval requirements in Atlantis

why

Gitlab Community Edition doesn't support approvals_before_merge so approval requirements in Atlantis won't work.

tests

n/a

references

• Initially discussed at Gitlab: apply_requirements not working < 15.6 #3270 (comment) and fix(gitlab): Add backwards compatible mergability check #3277 (comment)

[jukie]

In addition to the docs update I'd also like to contribute an actual check somewhere in Atlantis and we can log something when an unsupported client is detected and attempts to use this feature. Where should that go?

[jamengual]

I do not know if we have a specific place to do that in he code other than the function were we catch the error.

[nitrocode]

Was this meant to be closed?

[nitrocode]

Oh i see this was closed due to this comment

#3277 (comment)

[jukie]

Yeah it's not needed, I realized after pushing that it's already had there.