[1.7.x] Fixed #22813 -- Updated Pillow URL in documentation

Backport of dfa3505ff1 from master.

docs/ref/forms/fields.txt

@@ -633,7 +633,7 @@ For each field, we describe the default widget used if you don't specify
     When you use an ``ImageField`` on a form, you must also remember to
     :ref:`bind the file data to the form <binding-uploaded-files>`.
 
-.. _Pillow: http://python-imaging.github.io/Pillow/
+.. _Pillow: http://pillow.readthedocs.org/en/latest/
 .. _Python Imaging Library: http://www.pythonware.com/products/pil/
 
 ``IntegerField``

docs/ref/models/fields.txt

@@ -843,7 +843,7 @@ optional arguments:
 
 Requires the `Pillow`_ library.
 
-.. _Pillow: http://python-imaging.github.io/Pillow/
+.. _Pillow: http://pillow.readthedocs.org/en/latest/
 
 By default, :class:`ImageField` instances are created as ``varchar(100)``
 columns in your database. As with other fields, you can change the maximum