allscenarios-image-extra: Drop package-management image feature

Having a runtime package management tool on a read-only filesystsem
doesn't help much. We could support something in that regards for
development mode but at this point we don't have a defined story for it.
So let's drop it to not confuse users.

Fixes: https://git.ostc-eu.org/OSTC/OHOS/meta-ohos/-/issues/148


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