[Docs] Remove chardet mock to fix requests version check

* chardet is an easily installed pure python module so doesn't need mocking.

docs/source/conf.py

@@ -59,7 +59,7 @@ class Mock(object):
 
 MOCK_MODULES = ['deluge.ui.gtkui.gtkui', 'deluge._libtorrent',
                 'libtorrent', 'psyco',
-                'pygtk', 'gtk', 'gobject', 'gtk.gdk', 'pango', 'cairo', 'pangocairo', 'chardet']
+                'pygtk', 'gtk', 'gobject', 'gtk.gdk', 'pango', 'cairo', 'pangocairo']
 
 for mod_name in MOCK_MODULES:
     sys.modules[mod_name] = Mock()

tox.ini

@@ -177,8 +177,6 @@ deps =
     {[testenv]deps}
     sphinx
     sphinxcontrib-napoleon
-# Pin requests version due to bug: https://github.com/requests/requests/issues/4125
-    requests==2.15.1
 whitelist_externals =
     {[testenv]whitelist_externals}