Convert h2s to h1s where obvious

bookwyrm/templates/notifications.html

@@ -2,7 +2,7 @@
 {% load humanize %}l
 {% block content %}
 <div class="block">
-    <h2 class="title">Notifications</h2>
+    <h1 class="title">Notifications</h1>
 
     <form name="clear" action="/clear-notifications" method="POST">
         {% csrf_token %}