remove old config parameters if they are not used

Remove the following if they are not used:

max_object_size (site)
The maximum size of an object in GB (default: 5GB)
multipart_uploads (site)
Does the service support multipart uploads (True/False, default: False)
ranged_downloads (site)
Does the service support ranged downloads? (True/False, default: False)

They are also referenced in the manpage.