css: ensure dtext is always wrapped in .prose container.

Ensure dtext is always wrapped in a `<div class="prose">` or
`<span class="prose">` (for inline dtext) container so that dtext css is
properly applied.

app/views/users/_ban_notice.html.erb

@@ -1,5 +1,5 @@
 <div class="ui-corner-all ui-state-error" id="ban-notice">
   <h1>Your account has been temporarily banned</h1>
-  <p>Reason: <%= format_text CurrentUser.user.recent_ban.reason %></p>
+  <p>Reason: <span class="prose"><%= format_text CurrentUser.user.recent_ban.reason, inline: true %></span></p>
   <p>Your ban will expire in <%= time_ago_in_words(CurrentUser.user.recent_ban.expires_at) %></p>
 </div>

app/views/users/_statistics.html.erb

@@ -38,7 +38,11 @@
       <% if user.is_banned? && user.recent_ban %>
         <tr>
           <th>Ban reason</th>
-          <td><%= format_text presenter.ban_reason %></td>
+          <td>
+            <div class="prose">
+              <%= format_text presenter.ban_reason %>
+            </div>
+          </td>
         </tr>
       <% end %>