[FLEDGE] Don't treat lone negative score as error in component auctions.

When seller scripts want to reject an ad, they can return a negative
score (or 0). Before this CL, in a component auction, it was treated as
an error if they didn't return those scores in an object that had an
`allowComponentAuction` value of true. This CL makes setting
`allowComponentAuction` unnecessary - seller scripts can now just
return a score <= 0 directly to reject a bid without printing an error.

Note that this has no effect on the winner of an auction, as both
errors and scores <= 0 meant the bid being scored couldn't win. All it
does is avoid printing an error, and result in not throwing away debug
report URLs when component seller worklets return scores <= 0 without
setting `allowComponentAuction` to true.

Bug: None
Change-Id: Ie55762b7404b99407f79a5281c6a1c75a9b77449
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4956815
Reviewed-by: Caleb Raitto <caraitto@chromium.org>
Commit-Queue: Matt Menke <mmenke@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1213559}