Remove implementation implementation for DisableBoostPriority feature

The experiment will be redesigned with new arms following the analysis
of the results. Each of the next CLs in the stack adds a new policy that
can be activated with a new param for the feature.

Bug: 395914024, 483650343
Change-Id: If85a4f200ac62a1415e72e24d51e22f233260447
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7794885
Commit-Queue: Andres Ricardo Perez Rojas <andresrperez@chromium.org>
Reviewed-by: Patrick Monette <pmonette@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1628717}
NOKEYCHECK=True
GitOrigin-RevId: e9ef29bbaa9cea2e82ad0d2b03472b0888cad868