Fix disambiguation page that were never properly migrated from 1.4

Fix disambiguation page that were never properly migrated from 1.4

mysql> explain SELECT 'Disambiguations' as type,la.pl_namespace AS namespace,
       la.pl_title AS title, la.pl_from AS link_from
       FROM `pagelinks` AS la, `pagelinks` AS lb, `page` AS pa, `page` AS pb
       WHERE pb.page_namespace = 4
       AND pb.page_title = 'Liens_aux_pages_d\'homonymie'
       AND lb.pl_title = pb.page_title
       AND pa.page_id = lb.pl_from
       AND la.pl_title = pa.page_title;
---+------+----------+----------+-----+-----------+----+--------------+
tab|type  |possible k|key       |k_len|ref        |rows|Extra         |
---+------+----------+----------+-----+-----------+----+--------------+
pb |const |name_title|name_title|  259|const,const|   1|index         |
la |index |NULL      |pl_from   |  263|NULL       |1976|index         |
lb |index |pl_from   |pl_from   |  263|NULL       |1976|where & index |
pa |eq_ref|PRIMARY   |PRIMARY   |    4|lb.pl_from |   1|where         |
---+------+----------+----------+-----+-----------+----+--------------+