Fix invalid protected environment access levels

What does this MR do and why?

Rerun the migration from Cleanup invalid deploy access levels for protec... (!110686 - merged) with a few modifications

We needed to do that because we didn't have the model validation, and after Cleanup invalid deploy access levels for protec... (!110686 - merged) was merged users were able to create a few invalid records:

[ gprd ] production> ProtectedEnvironments::DeployAccessLevel.where("user_id IS NOT NULL AND group_id IS NOT NULL").count
=> 0
[ gprd ] production> ProtectedEnvironments::DeployAccessLevel.where("user_id IS NOT NULL AND access_level IS NOT NULL").count
=> 2
[ gprd ] production> ProtectedEnvironments::DeployAccessLevel.where("group_id IS NOT NULL AND access_level IS NOT NULL").count
=> 0

So we wouldn't be able to introduce the database constraint for this. After Validate ProtectedEnvironments::DeployAccessLev... (!114449 - merged) we can merge this one and we won't have invalid records in the database.

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Related to #330483 (closed)