Recent changes in swh-scheduler add new parameters to the celery tasks
produced from swh.scheduler.model.ListedOrigin instances.
So ensure to handle any new parameters by not hardcoding the expected
ones in task signatures.
Also remove explicit setting of visit_date if none has been provided
as task parameter as it is already handled in loader constructor.
Add new tests checking task parameters produced from ListedOrigin
instances do no raise error when attempting to create a git loader.
Related to T4187