ENGCOM-621: Fix grammar in demo store notice #13877

 - Merge Pull Request magento/magento2#13877 from erikhansen/magento2:patch-2
 - Merged commits:
   1. bc6aaee
   2. aa3a488

Author: magento-engcom-team

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

@@ -107,7 +107,7 @@ Remove,Remove
 "For the best experience on our site, be sure to turn on Javascript in your browser.","For the best experience on our site, be sure to turn on Javascript in your browser."
 "Local Storage seems to be disabled in your browser.","Local Storage seems to be disabled in your browser."
 "For the best experience on our site, be sure to turn on Local Storage in your browser.","For the best experience on our site, be sure to turn on Local Storage in your browser."
-"This is demo store. No orders will be fulfilled.","This is demo store. No orders will be fulfilled."
+"This is a demo store. No orders will be fulfilled.","This is a demo store. No orders will be fulfilled."
 "Items %1 to %2 of %3 total","Items %1 to %2 of %3 total"
 "%1 Item","%1 Item"
 "%1 Item(s)","%1 Item(s)"

app/code/Magento/Theme/view/frontend/templates/html/notices.phtml

@@ -54,7 +54,7 @@ require(['jquery'], function(jQuery){
 <?php if ($block->displayDemoNotice()): ?>
     <div class="message global demo">
         <div class="content">
-            <p><?= /* @escapeNotVerified */ __('This is demo store. No orders will be fulfilled.') ?></p>
+            <p><?= /* @escapeNotVerified */ __('This is a demo store. No orders will be fulfilled.') ?></p>
         </div>
     </div>
 <?php endif; ?>