Fields are sometimes marked as required when they are not

Merging https://github.com/thoughtbot/administrate/pull/1521 gave Administrate the ability to detect "required" fields and mark them as such.

However, this detection is not always perfect. On occasion, there will be :if/:unless conditions attached to the validation rule. These are not correctly interepreted by Administrate. So for example:

  validates :amount, :currency, presence: true, if: ->{ stripe? }

Originally posted by @sedubois in https://github.com/thoughtbot/administrate/pull/1521#issuecomment-708506703