Update idlharness test expectations for WebTransport

This CL is a follow-up to https://chromium-review.googlesource.com/c/chromium/src/+/3144590,
as it makes sure all the idlharness tests are run and pass, instead of
just skipping them. The relevant test expected.txt files have also been
updated.

Bug: 1201569
Change-Id: I1acbb308116ebf9f1c8bfa4cd30ea238a60203b1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3143837


Commit-Queue: Nidhi Jaju <nidhijaju@chromium.org>
Reviewed-by: Kenichi Ishibashi <bashi@chromium.org>
Cr-Commit-Position: refs/heads/main@{#919123}