Removing vboot 1.0 verity metadata

The generic system.img shouldn't contain any specific verity metadata
because we don't mandate how to do verified boot. Plus, OC-DR devices
use AVB instead of vboot 1.0.

Bug: 62647718
Test: Boot a DR device with the generic system.img
Change-Id: I0966d88d4512621cce7b8abdc28a90a6e312a391