Use unicast instead of broadcast as ethernet destination in `test_apf_drop_ethercat`

To prevent packet dropped earlier by multicast filtering,
use unicast ethernet destination instead

Bug: 360730207
Test: m connectivity_multi_devices_snippet && atest CtsConnectivityMultiDevicesTestCases:ApfV4Test
Change-Id: I4816b71f68f349abf1423c7013bb058ccc233d61
2 files changed