ENGCOM-6780: #26612 Fix failure on Coupon Apply procedure when loading mask still visible #26614

 - Merge Pull Request #26614 from lbajsarowicz/magento2:bugfix/26612-coupon-failure
 - Merged commits:
   1. c13b83f

Author: magento-engcom-team

app/code/Magento/Checkout/Test/Mftf/Test/StorefrontApplyPromoCodeDuringCheckoutTest.xml

@@ -54,7 +54,7 @@
             <argument name="shippingMethod" value="Flat Rate"/>
         </actionGroup>
 
-         <!-- Click Apply Discount Code: section is expanded. Input promo code, apply and see success message -->
+        <!-- Click Apply Discount Code: section is expanded. Input promo code, apply and see success message -->
         <actionGroup ref="StorefrontApplyDiscountCodeActionGroup" stepKey="applyCoupon">
             <argument name="discountCode" value="$$createCouponForCartPriceRule.code$$"/>
         </actionGroup>

app/code/Magento/SalesRule/Test/Mftf/ActionGroup/StorefrontApplyDiscountCodeActionGroup.xml

@@ -16,6 +16,7 @@
         <fillField selector="{{DiscountSection.DiscountInput}}" userInput="{{discountCode}}" stepKey="fillFieldDiscountCode"/>
         <click selector="{{DiscountSection.ApplyCodeBtn}}" stepKey="clickToApplyDiscount"/>
         <waitForElement selector="{{DiscountSection.DiscountVerificationMsg}}" time="30" stepKey="waitForDiscountToBeAdded"/>
+        <waitForLoadingMaskToDisappear stepKey="waitForLoadingFinished"/>
         <see selector="{{DiscountSection.DiscountVerificationMsg}}" userInput="Your coupon was successfully applied" stepKey="assertDiscountApplyMessage"/>
     </actionGroup>
 </actionGroups>