Remove unnecessary span class "debate-comments".
We take advantage of this commit to also unify the format of the date
that appears next to the comments with the rest of the application. The
format that we removed is being used on the same page in the
"Participation phases" tab (I guess that was the reason for putting it
the same) but I think it makes more sense to use the date format that is
used in this kind section in the rest of the application.
0ca17c6fae