remove 'backing track uploads not implemented' doc

html/index.html

@@ -852,14 +852,6 @@ <h3>I keep seeing "Due to lag, your singing is not included"</h3>
 This happens most often if your computer is overloaded. Try closing
 other things running on your computer, including background tabs.
 
-<h3>I can't figure out how to upload a backing track</h3>
-
-Currently, the only way to upload a backing track is to email it to me
-and I can upload it: <tt>[email protected]</tt>.  This is
-silly, and I should make it better. Tracking this in <a
-target=_blank href="https://github.com/gwillen/solstice-audio-test/issues/89">Issue
-89</a>.</a>
-
 <h3>Something else weird is going on</h3>
 
 If you'd like Jeff to drop into your call and have a look, you're