Remove useless test header setup for emails

Once upon a time we needed a helper to set the `from` header of emails.
This is now set in the ApplicationMailer and not necessary any more.

spec/models/order_cycle_spec.rb

@@ -3,8 +3,6 @@
 require 'spec_helper'
 
 describe OrderCycle do
-  include OpenFoodNetwork::EmailHelper
-
   it "should be valid when built from factory" do
     expect(build(:simple_order_cycle)).to be_valid
   end
@@ -448,9 +446,6 @@ describe OrderCycle do
       create(:completed_order_with_totals, distributor: shop, user: user, order_cycle: oc)
     }
 
-    before do
-      setup_email
-    end
     before { order_cancelled.cancel }
 
     it "only returns items from non-cancelled orders in the OC, placed by the user at the shop" do

spec/models/spree/order_spec.rb

@@ -3,8 +3,6 @@
 require 'spec_helper'
 
 describe Spree::Order do
-  include OpenFoodNetwork::EmailHelper
-
   let(:user) { build(:user, email: "spree@example.com") }
   let(:order) { build(:order, user: user) }
 
@@ -909,10 +907,6 @@ describe Spree::Order do
 
   describe "scopes" do
     describe "not_state" do
-      before do
-        setup_email
-      end
-
       it "finds only orders not in specified state" do
         o = FactoryBot.create(:completed_order_with_totals,
                               distributor: create(:distributor_enterprise))

spec/models/spree/user_spec.rb

@@ -84,8 +84,6 @@ describe Spree::User do
 
   context "#create" do
     it "should send a confirmation email" do
-      setup_email
-
       performing_deliveries do
         expect do
           create(:user, email: 'new_user@example.com', confirmation_sent_at: nil, confirmed_at: nil)
@@ -118,8 +116,6 @@ describe Spree::User do
 
   context "confirming email" do
     it "should send a welcome email" do
-      setup_email
-
       expect do
         create(:user, confirmed_at: nil).confirm
       end.to enqueue_job ActionMailer::MailDeliveryJob