Removing unneeded from __future__ import statements.

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

ebook_converter/ebooks/conversion/plugins/oeb_output.py

@@ -1,9 +1,3 @@
-from __future__ import absolute_import, division, print_function, unicode_literals
-
-__license__ = 'GPL 3'
-__copyright__ = '2009, Kovid Goyal <kovid@kovidgoyal.net>'
-__docformat__ = 'restructuredtext en'
-
 import os, re
 
 
@@ -12,6 +6,11 @@ from ebook_converter.customize.conversion import (OutputFormatPlugin,
 from ebook_converter import CurrentDir
 
 
+__license__ = 'GPL 3'
+__copyright__ = '2009, Kovid Goyal <kovid@kovidgoyal.net>'
+__docformat__ = 'restructuredtext en'
+
+
 class OEBOutput(OutputFormatPlugin):
 
     name = 'OEB Output'