Move auth-popup instruction into checkout module

Author: vovayatsyuk

app/code/Magento/Checkout/view/frontend/layout/checkout_index_index.xml

@@ -445,5 +445,6 @@
             </block>
         </referenceContainer>
         <referenceContainer name="page.messages" remove="true"/>
+        <referenceBlock name="authentication-popup" remove="true"/>
     </body>
 </page>