Update vts_generic_boot_image_test for new init_boot partition

For GKI devices launching with T+, the generic ramdisk will be in this
new init_boot partition instead of the boot partition.

Test: atest vts_generic_boot_image_test
Bug: 203698939
Change-Id: Ie0eb0859636b911f6b3b3fcf0023bb80f2ddf581
1 file changed