Fixed a typo in 1.6 release notes.

docs/releases/1.6.txt

@@ -1183,7 +1183,7 @@ create a ``ModelForm`` that uses all fields for a model.
 For this reason, if you use these views for editing models, you must also supply
 the ``fields`` attribute (new in Django 1.6), which is a list of model fields
 and works in the same way as the :class:`~django.forms.ModelForm`
-``Meta.fields`` attribute. Alternatively, you can set set the ``form_class``
+``Meta.fields`` attribute. Alternatively, you can set the ``form_class``
 attribute to a ``ModelForm`` that explicitly defines the fields to be used.
 Defining an ``UpdateView`` or ``CreateView`` subclass to be used with a model
 but without an explicit list of fields is deprecated.