Move template guidance underneath

Two problems with having it on the side:
- some users didn’t see it at all
- there wasn’t space to have additional guidance about Markdown-style
  formatting

app/templates/views/edit-sms-template.html

@@ -25,8 +25,7 @@
             delete_link_text='Delete this template'
           ) }}
         </div>
-        <aside class="column-one-third">
-          <h2 style="margin: 0 0 5px 0;">Help</h2>
+        <aside class="column-whole">
           {% include "partials/templates/guidance-personalisation.html" %}
           {% include "partials/templates/guidance-links.html" %}
           {% include "partials/templates/guidance-character-count.html" %}