bootimg-pcbios-label.py: Remove wic plugin

We revert this workaround as the existing poky plugin,
bootimg-pcbios.py, includes the needed support as per the last poky bump
in the manifest repository.

PartOf: https://git.ostc-eu.org/OSTC/OHOS/meta-ohos/-/issues/97



Signed-off-by: Andrei Gherzan <andrei.gherzan@huawei.com>