Fix bugfix note

This fixes a bugfix note that was added because of #1293, which
pointed out that a change in a bugfix [1] broke backwards
compatibility.  The bugfix did not work as expected because a
variable was quoted when it should not have been.  This removes
the quotes around the variable, which brings back the expected
functionality.

docs/topics/release-notes.md

@@ -98,7 +98,7 @@ You can determine your currently installed version using `pip freeze`:
 
     class DisablePaginationMixin(object):
         def get_paginate_by(self, queryset=None):
-            if self.request.QUERY_PARAMS['self.paginate_by_param'] == '0':
+            if self.request.QUERY_PARAMS[self.paginate_by_param] == '0':
                 return None
             return super(DisablePaginationMixin, self).get_paginate_by(queryset)