Revert "Update PayFast docs."

This reverts commit 45cc380c6d9f964ab8608ce85600e3c2002542a0.
Revert "Check for required fields in the PayFast integration."

This reverts commit 1d19224e7ab7b51ae9e3487d73e110933ebc5943.
Revert "Update PayFast integration."

This reverts commit dade5ff8f9c6725253e3a504c9562be4f0159620.