Added versionadded annotations for redirect middleware attributes.

refs #19321

docs/ref/contrib/redirects.txt

@@ -89,6 +89,8 @@ Middleware
 
     .. attribute:: response_gone_class
 
+        ..  versionadded:: 1.7
+
         The :class:`~django.http.HttpResponse` class used when a
         :class:`~django.contrib.redirects.models.Redirect` is not
         found for the requested path or has a blank ``new_path``
@@ -98,6 +100,8 @@ Middleware
 
     .. attribute:: response_redirect_class
 
+        ..  versionadded:: 1.7
+
         The :class:`~django.http.HttpResponse` class that handles the
         redirect.