bin/post_release.py: Add .html to hrefs

oops.

Fixes: 3226b12a09bbcbd25526fd6da6257057d26ddb31
       ("release: Add an update_release_calendar.py script")
Reviewed-by: Eric Engestrom <eric@engestrom.ch>
Reviewed-by: Juan A. Suarez <jasuarez@igalia.com>
1 file changed