new_variant: update links in documentation

The document "Working with coreboot Upstream and Chromium" moved from
drive to the Chromium docs, so update the link. Add a link to the
Wyvern tutorial video.

BUG=None
TEST=N/A

Change-Id: If5e1e6208d0b8ae3117f2795e2b7fd9faa3c877f
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/2321301
Tested-by: Paul Fagerburg <pfagerburg@chromium.org>
Auto-Submit: Paul Fagerburg <pfagerburg@chromium.org>
Reviewed-by: Jack Rosenthal <jrosenth@chromium.org>
Commit-Queue: Jack Rosenthal <jrosenth@chromium.org>
1 file changed