Removing unneeded from __future__ import statements.

Since we are on Python 3.6 and up, we don't need those anymore.

ebook_converter/utils/html2text.py

@@ -1,9 +1,3 @@
-#!/usr/bin/env python2
-# vim:fileencoding=utf-8
-# License: GPLv3 Copyright: 2019, Kovid Goyal <kovid at kovidgoyal.net>
-from __future__ import absolute_import, division, print_function, unicode_literals
-
-
 def html2text(html):
     from html2text import HTML2Text
     import re