MAGETWO-71833: Grammar fix for #9533 #10627

 - Merge Pull Request #10627 from coolblueweb/magento2:fix/authentication_popup_typo
 - Merged commits:
   1. c7de684

app/code/Magento/Customer/i18n/en_US.csv

@@ -400,12 +400,12 @@ Password:,Password:
 "If you did not make this request, you can ignore this email and your password will remain the same.","If you did not make this request, you can ignore this email and your password will remain the same."
 "Your %store_name password has been changed","Your %store_name password has been changed"
 "We have received a request to change the following information associated with your account at %store_name: password.","We have received a request to change the following information associated with your account at %store_name: password."
-"Checkout out as a new customer","Checkout out as a new customer"
+"Checkout as a new customer","Checkout as a new customer"
 "Creating an account has many benefits:","Creating an account has many benefits:"
 "See order and shipping status","See order and shipping status"
 "Track order history","Track order history"
 "Check out faster","Check out faster"
-"Checkout out using your account","Checkout out using your account"
+"Checkout using your account","Checkout using your account"
 "Email Address","Email Address"
 "Are you sure you want to do this?","Are you sure you want to do this?"
 "Are you sure you want to delete this address?","Are you sure you want to delete this address?"

app/code/Magento/Customer/view/frontend/web/template/authentication-popup.html

@@ -14,7 +14,7 @@
             <strong id="block-new-customer-heading"
                     role="heading"
                     aria-level="2"
-                    data-bind="i18n: 'Checkout out as a new customer'"></strong>
+                    data-bind="i18n: 'Checkout as a new customer'"></strong>
         </div>
         <div class="block-content" aria-labelledby="block-new-customer-heading">
             <p data-bind="i18n: 'Creating an account has many benefits:'"></p>
@@ -39,7 +39,7 @@
             <strong id="block-customer-login-heading"
                     role="heading"
                     aria-level="2"
-                    data-bind="i18n: 'Checkout out using your account'"></strong>
+                    data-bind="i18n: 'Checkout using your account'"></strong>
         </div>
         <!-- ko foreach: getRegion('messages') -->
         <!-- ko template: getTemplate() --><!-- /ko -->