mix mobilizon.instance gen instance-name argument

When using mix mobilizon.instance gen --instance-name TOTO

instance-name argument is not take in count... => https://paste.yunohost.org/amulodujex.scala

https://framagit.org/framasoft/mobilizon/-/blob/master/lib/mix/tasks/mobilizon/instance.ex#L82, seems like the option would be --name