Revert change made in https://github.com/openfoodfoundation/openfoodnetwork/pull/12538

Although the change fix the issue in the back office scenario, it has
the side effect of getting the order total out of sync. Updating a
payment adjustment need to be followed by udpating the order total and
payment amount to keep everything in sync.

app/models/spree/payment.rb

@@ -155,7 +155,6 @@ module Spree
       if adjustment
         adjustment.originator = payment_method
         adjustment.label = adjustment_label
-        adjustment.amount = payment_method.compute_amount(self)
         adjustment.save
       elsif !processing_refund? && payment_method.present?
         payment_method.create_adjustment(adjustment_label, self, true)

spec/system/admin/order_spec.rb

@@ -180,6 +180,7 @@ RSpec.describe '
     let(:order_with_fees) { create(:completed_order_with_fees, user:, distributor:, order_cycle: ) }
 
     it 'recalculates transaction fee' do
+      pending
       login_as_admin
       visit spree.edit_admin_order_path(order_with_fees)