Revert "unpack_bootimg: Export 'vendor_ramdisk' for vendor_boot v4" am: f85a2fd564 am: ccf44dde20 am: fa9f1fa517 am: a6cff18639

Original change: https://android-review.googlesource.com/c/platform/system/tools/mkbootimg/+/2181573

Change-Id: Id6b1bdd0a263a05441d003efb166ad44dc4dbf28
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>