[FIX] mail: disable fetchmail servers on neutralize

When neutralizing the database we should disactivate all
fetchmail servers to prevent data loss (ex. when using POP)

opw-2758998

closes odoo/odoo#132379

Signed-off-by: Nicolas Martinelli (nim) <nim@odoo.com>

addons/mail/data/neutralize.sql

 -- deactivate mail template
 UPDATE mail_template
    SET mail_server_id = NULL;
+-- deactivate fetchmail server
+UPDATE fetchmail_server
+   SET active = false;