Dynamic tiering is now enabled by default, and the origin trial is
expired, so the callback can be removed.
The callback was already never called, because the flag value is always
checked first.

R=ahaas@chromium.org, mlippautz@chromium.org

Bug: v8:12281
Change-Id: I58eaa210c86024128328a13ba07bb8fc1b437841
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3644951
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80633}