test: drop removed SCSI passthrough feature

test: drop removed SCSI passthrough feature

This feature has been deprecated since QEMU 5.0 and finally removed in
QEMU 9.1 [0] which now causes issues when running the storage tests on
latest Arch:

------ testcase_long_sysfs_path: BEGIN ------
...
qemu-system-x86_64: -device virtio-blk-pci,drive=drive0,scsi=off,bus=pci_bridge25: Property 'virtio-blk-pci.scsi' not found
E: qemu failed with exit code 1

[0] https://github.com/qemu/qemu/commit/a271b8d7b2f39275a05e49deb7c8edc20b7a8279

(cherry picked from commit cd57920fbf6a8f7769a82cfc9bebc12965de0199)