[1.7.x] Fixed signature of ModelAdmin.get_paginator() in docs.

Backport of ecf4ed2 from master

docs/ref/contrib/admin/index.txt

@@ -1694,7 +1694,7 @@ templates used by the :class:`ModelAdmin` views:
     documentation for more details. One difference is that the level may be
     passed as a string label in addition to integer/constant.
 
-.. method:: ModelAdmin.get_paginator(queryset, per_page, orphans=0, allow_empty_first_page=True)
+.. method:: ModelAdmin.get_paginator(request, queryset, per_page, orphans=0, allow_empty_first_page=True)
 
     Returns an instance of the paginator to use for this view. By default,
     instantiates an instance of :attr:`paginator`.