[task] Remove explicit TimeTicks in ThreadController active.

This was introduced in https://chromium-review.googlesource.com/c/chromium/src/+/3645137
Explicit TimeTicks were used to align the event with the async phases.
Providing explicit TimeTicks means thread time is no longer recorded,
which renders cpu metrics in telemetry invalid.

This CL removes the explicit TimeTicks until we find a better way to
have the phase events aligned.


Bug: 1355021
Change-Id: I261c050599b1d69b9f9ce0f82589248c135f524a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3861489
Reviewed-by: Francois Pierre Doray <fdoray@chromium.org>
Commit-Queue: Etienne Pierre-Doray <etiennep@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1042564}