The intial version of the API was replaced with a more ergonomic one
recently.

We can also safely remove the test as the new API guarantees that
tasks are always finished and cancelled.

Bug: chromium:1334585
Change-Id: I9ff8b92fcd73ef821c86de52c40a1d04b15ea918
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3780539Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Simon Zünd <szuend@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81950}