Fix cost condition in DetrHungarianMatcher and YolosHungarianMatcher to allow zero-cost

[kongzii]

What does this PR do?

Fixes costs condition in DetrHungarianMatcher and YolosHungarianMatcher. In #16720 a bug was introduced while switching from asserts to conditions. Currently, any zero-cost will result in a ValueError:

if class_cost == 0 or bbox_cost == 0 or giou_cost == 0:
    raise ValueError("All costs of the Matcher can't be 0")

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Did you read the contributor guideline,
  Pull Request section?
• Was this discussed/approved via a Github issue or the forum? Please add a link
  to it if that's the case.
• Did you make sure to update the documentation with your changes? Here are the
  documentation guidelines, and
  here are tips on formatting docstrings.
• Did you write any new necessary tests?

Who can review?

@LysandreJik @sgugger based on reviewers of previous PR #16720.

[HuggingFaceDocBuilderDev]

The documentation is not available anymore as the PR was closed or merged.

[LysandreJik]

This looks reasonable given the error message! cc @NielsRogge

[sgugger]

Indeed, this slipped through the cracks of my review of #16720. Thanks a lot for fixing!