Double quotes for i18n string

cms/templates/activation_invalid.html

@@ -15,7 +15,7 @@
 
     <div class="notice notice-incontext notice-instruction has-actions">
       <div class="msg">
-        <h1 class="title">${_('Your account activation is invalid')}</h1>
+        <h1 class="title">${_("Your account activation is invalid")}</h1>
         <div class="copy">
           <p>${_("We're sorry. Something went wrong with your activation. Check to make sure the URL you went to was correct &mdash; e-mail programs will sometimes split it into two lines.")}</p>
           <p>${_("If you still have issues, contact edX Support. In the meantime, you can also return to {link_start}the Studio homepage.{link_end}").format(