bug(content): Page would not render properly in some cases

Because:
- There appeared to be invalid html

This Commit:
- Fixes the mismatched <span>Learn more</a> html
- Fixes bad div tag
- Corrects className to be class.
- Adds extra fixes include for brandMessaging. It needs `{{{` not `{{`

packages/fxa-content-server/app/scripts/templates/partial/brand-messaging.mustache

@@ -3,7 +3,7 @@
     <div class="banner-brand-message w-full">
         <div class="flex justify-center p-2 brand-banner-bg">
             {{#showPrelaunch}}
-            <div class="flex"/>
+            <div class="flex">
                 <div class="flex-none relative">
                     <img
                         class="w-8 h-8 bg-black m-4 mt-1"
@@ -17,17 +17,17 @@
                     </p>
                     <p class="text-start text-xs">
                         {{#t}}You’ll still sign in with the same username and password, and there are no other changes to the products that you use.{{/t}}
-                        <span role="link" tabindex="0" class="brand-learn-more cursor-pointer underline">{{#t}}Learn more{{/t}}</a>
+                        <span role="link" tabindex="0" class="brand-learn-more cursor-pointer underline">{{#t}}Learn more{{/t}}</span>
                     </p>
                 </div>
             </div>
             {{/showPrelaunch}}
             {{#showPostlaunch}}
-            <div className="flex"/>
+            <div class="flex"/>
                 <div>
                     <p class="text-sm font-bold">
                         {{#t}}We’ve renamed Firefox accounts to Mozilla accounts. You’ll still sign in with the same username and password, and there are no other changes to the products that you use.{{/t}}
-                        <span role="link" tabindex="0" class="brand-learn-more cursor-pointer underline">{{#t}}Learn more{{/t}}</a>
+                        <span role="link" tabindex="0" class="brand-learn-more cursor-pointer underline">{{#t}}Learn more{{/t}}</span>
                     </p>
                 </div>
             </div>

packages/fxa-content-server/app/scripts/templates/post_verify/third_party_auth/set_password.mustache

@@ -1,4 +1,4 @@
-{{ brandMessagingHTML }}
+{{{ brandMessagingHTML }}}
 <div class="card">
   <header class="mb-2">
     <h1 id="fxa-signup-password-header" class="card-header">