Revert "unpack_bootimg: Export 'vendor_ramdisk' for vendor_boot v4"

This reverts commit 33bf962400b09c58e20418494597efb19952f509.

Reason for revert: not needed anymore, and it breaks b/240591121

Change-Id: Ic43edfa548384e1a02b5cab884d95a40bf32589f
1 file changed