Removing unneeded from __future__ import statements.

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

ebook_converter/ebooks/BeautifulSoup.py

@@ -1,9 +1,4 @@
-#!/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
-
 import bs4
 from bs4 import (  # noqa
     CData, Comment, Declaration, NavigableString, ProcessingInstruction,