[fix] Remove useless `email_legacy` conf_regen hook
[fix] Remove useless `email_legacy` conf_regen hook

The file `/etc/yunohost/ervices.yml` is now updated thanks to 0bacf65,
allowing to add new services and remove old ones.
Moreover, while migrating to new YunoHost version, the user should execute
`apt-get autoremove` to remove old packages such as spamassassin, amavis and
postgrey. This sounds more reliable and allows to get rid of this useless hook
which would be executed for ever, trying to stop already removed services.

YunoHost/yunohost,YunoHost/moulinette-yunohost,YunoHost/moulinette-yunohost,YunoHost/moulinette-yunohost,YunoHost/yunohost,YunoHost/yunohost,YunoHost/yunohost,YunoHost/moulinette-yunohost,YunoHost/moulinette-yunohost