Remove outdated comment in tox.ini

https://code.djangoproject.com/ticket/28679 has been merged, the build
should pass on Django master.

Keep ignoring failures because Django master's API might not be stable
and docs not published yet; thus this does only have informational
value.

Author: francoisfreitag

tox.ini

@@ -18,6 +18,5 @@ deps =
     djangomaster: https://github.com/django/django/archive/master.tar.gz
     .[test]
 
-# Waiting on upstream fix for https://code.djangoproject.com/ticket/28679
 ignore_outcome =
     djangomaster: True