[1.6.x] Corrected example code for get_query_set upgrade in 1.6 release notes

The conditional setting of `get_query_set` is required for correct behaviour
if running Django 1.8. The full gory details are here:

http://lukeplant.me.uk/blog/posts/handling-django%27s-get_query_set-rename-is-hard/

Backport of f87e552d98 from master

docs/releases/1.6.txt

@@ -1133,7 +1133,8 @@ a ``get_queryset_compat`` method as below and use it internally to your manager:
         def get_queryset(self):
             return YourCustomQuerySet() # for example
 
-        get_query_set = get_queryset
+        if django.VERSION < (1, 6):
+            get_query_set = get_queryset
 
         def active(self): # for example
             return self.get_queryset_compat().filter(active=True)