Remove export parameters from documentation

[PietrH]

The parameters passed to the export endpoint don't do anything, so they are best removed from the API.

We chose to not have any parameters in the export

https://uat-db.vespawatch.be/observations/export/?municipality_id=95

Doesn't actually return obserservations from municipality 95 only, but rather returns everything. This is fine.

But the swagger docs show parameters:

These should be removed so it's clear you can't pass any.

[PietrH]

They are still there.

[PietrH]

The swagger docs return a HTTP 500

https://uat-db.vespawatch.be/swagger/