Reland "futility: Remove legacy bios.bin name"

This is a reland of commit 20fc7f70b1b4 ("futility: Remove legacy
bios.bin name"). Compared to that commit (CL:7883122), test_update.sh is
fixed.

Original change's description:
> futility: Remove legacy bios.bin name
>
> Remove the legacy "bios.bin" name from the firmware updater output
> mode. Also remove the fallback check for "bios.bin" when building a
> manifest from a simple folder.
>
> BUG=b:517029427
> TEST=make runtests -j
> BRANCH=none
>
> Cq-Depend: chromium:7877775
> Change-Id: I04e8a7c4c3c1a186eaf02c204718b42b919835c9
> Signed-off-by: Yu-Ping Wu <yupingso@google.com>
> Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/7883122
> Auto-Submit: Yu-Ping Wu <yupingso@chromium.org>
> Commit-Queue: Yu-Ping Wu <yupingso@chromium.org>
> Tested-by: Yu-Ping Wu <yupingso@chromium.org>
> Reviewed-by: Jakub "Kuba" Czapiga <czapiga@google.com>

BUG=b:517029427
TEST=make runfutiltests
BRANCH=none

Change-Id: I811c19821c204f874133e6ec6db5631fd94e799d
Signed-off-by: Yu-Ping Wu <yupingso@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/7925126
Reviewed-by: Jakub "Kuba" Czapiga <czapiga@google.com>
Commit-Queue: Yu-Ping Wu <yupingso@chromium.org>
Tested-by: Yu-Ping Wu <yupingso@chromium.org>