Update of the migration SQL file

I got rid of the `private` field in the table `dj_webapps`.
Signed-off-by: Matthieu Berjon <matthieu.berjon@inria.fr>

django/tools/migration2django.sql

@@ -262,7 +262,9 @@ ALTER TABLE `dj_users`
 -- Update of webapps table
 --
 
-ALTER TABLE `dj_webapps` CHANGE COLUMN `default_job_queue_id` `dj_job_queue_id` int(11) NOT NULL;
+ALTER TABLE `dj_webapps`
+  DROP COLUMN `private`;
+ALTER TABLE `dj_webapps` CHANGE COLUMN `default_job_queue_id` `job_queue_id` int(11) NOT NULL;
 
 --
 -- Update of jobs table