docs: forgot to remove vars for readme on local backups

roles/ynh_backup/README.md

@@ -30,8 +30,6 @@ ynh_backup:
   scheduled_month: "*"
   system: True
   apps: True
-  src_script: "templates/ynh_backup.sh.j2"
-  dest_script: "/usr/bin"
 ```
 
 - `ynh_backup.scheduled`: Enable the YunoHost applications backup feature by setting the value to `True`.