Drop arm64 probe test job
Drop arm64 probe test job

Most of the time, we're so resource constrained that we trip the
three-hour (!!) job timeout, while the x86_64 job can typically complete
within an hour. When the arm64 probe tests *do* fail, they've often
failed due to eventual-consistency problems; things like object-updaters
popping 10s timeouts and not getting asyncs off disk.

The job last passed back in January.

Change-Id: I31efa3fef673a5541505e4855e52bfd0c9668ffd

openstack/swift,tipabu/swift,tipabu/swift,openstack/swift,openstack/swift,tipabu/swift,tipabu/swift,openstack/swift