Don't pass owner= when spying on HostingServiceClient._make_form_data_boundary.
Review Request #1685 — Created June 27, 2019 and submitted
A recent change added `owner=` arguments to any `spy_on()` call that spied on an unbound method. One of these was actually a static method, and while this didn't break Python 2.7, it did break 3.x. This is a trivial fix to remove the `owner=` argument for this specific spy.