Remove the old (V5) WPT MANIFEST

Follow-up to https://crrev.com/c/1555413

Change-Id: I34e094eca9a1795d069d93ba58e97349896b3c4d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1565186
Reviewed-by: Luke Z <lpz@chromium.org>
Commit-Queue: Robert Ma <robertma@chromium.org>
Cr-Commit-Position: refs/heads/master@{#650396}
1 file changed