Audio post minor improvements.

- Make clear on post submission that users can upload audio.
 - Fix a missing closing </div> that was breaking submission.html
   on audio posts.

files/templates/submission.html

@@ -295,6 +295,7 @@
 									<div class="col">
 										<audio controls preload="none" src="{{p.realurl(v)}}"></audio>
 									</div>
+								</div>
 							{% endif %}
 							{{p.realbody(v) | safe}}
 

files/templates/submit.html

@@ -59,7 +59,7 @@
 														<input autocomplete="off" id="file-upload" accept="image/*, video/*, audio/*" type="file" name="file-url" {% if request.headers.get('cf-ipcountry')=="T1" %}disabled{% endif %} hidden>
 													</label>
 													<small class="form-text text-muted">Optional if you have text.</small>
-													<small class="form-text text-muted">You can upload images or videos.</small>
+													<small class="form-text text-muted">You can upload images, videos, or audio.</small>
 												</div>
 												</div>