[FIX] mail: allow to delete mail alias all employees

It was allowed for all employees to read, create and edit
mail aliases. Only the deletion was prevented.
Nevertheless, giving the possibility to rename a mail alias
is allmost seen as a deletion, as you can rename it to something
that just won't be used anymore. Therefore, we can consider
to give any employees the rights to delete mail aliases.

Besides, not allowing the unlink leads to issues when the
mail alias is associated to a record the user wants to delete.
He was able to create the record, and its mail aliases, but
he could not remove the record, as he was not allowed to remove
the mail alias.
For instance, an HR officer was able to create a job position,
with its mail alias, but couldn't remove the job position he created.

Closes #8466

addons/mail/security/ir.model.access.csv

@@ -13,7 +13,7 @@ access_mail_notification_system,mail.notification.system,model_mail_notification
 access_mail_group_all,mail.group.all,model_mail_group,,1,0,0,0
 access_mail_group_user,mail.group.user,model_mail_group,base.group_user,1,1,1,1
 access_mail_alias_all,mail.alias.all,model_mail_alias,,1,0,0,0
-access_mail_alias_user,mail.alias.user,model_mail_alias,base.group_user,1,1,1,0
+access_mail_alias_user,mail.alias.user,model_mail_alias,base.group_user,1,1,1,1
 access_mail_alias_system,mail.alias.system,model_mail_alias,base.group_system,1,1,1,1
 access_mail_message_subtype_all,mail.message.subtype.all,model_mail_message_subtype,,1,0,0,0
 access_mail_message_subtype_system,mail.message.subtype.system,model_mail_message_subtype,base.group_system,1,1,1,1