Fix Nightly release notes rendering (#14098)

* Fix reflow issue when a release note's content is shorter than a single line and there is a bug ID attached to the note

* Fix HTML validation error: divs not allowed in a hX element

bedrock/firefox/templates/firefox/releases/notes.html

@@ -133,8 +133,8 @@
       <div class="mzp-l-content mzp-has-sidebar mzp-l-sidebar-left">
         <div class="mzp-l-sidebar">
           <h2 class="c-release-summary">
-            <div class="c-release-version">{{ release.version }}</div>
-            <div class="c-release-product">{{ release.product }} {{ release.channel }}</div>
+            <span class="c-release-version">{{ release.version }}</span>
+            <span class="c-release-product">{{ release.product }} {{ release.channel }}</span>
           </h2>
           {% if release.is_public %}
             <p class="c-release-date">{{ release.release_date|l10n_format_date }}</p>

media/css/firefox/releasenotes.scss

@@ -168,6 +168,7 @@ $image-path: '/media/protocol/img';
 .c-release-version {
     @include font-base;
     @include text-title-xl;
+    display: block;
 }
 
 .c-release-first-text,
@@ -179,6 +180,7 @@ $image-path: '/media/protocol/img';
     .c-release-product {
         @include font-base;
         @include text-title-2xs;
+        display: block;
     }
 
     .c-release-date {
@@ -408,6 +410,10 @@ $image-path: '/media/protocol/img';
 }
 
 .release-note {
+    .release-note-content{
+        width: 100%;
+    }
+
     .bug-id {
         @include bidi(((text-align, right, left),));
         display: block;