Remove OnBeginFrameAcks

This was intended to reduce IPC usage, especially for lacros. However
due to other inherent issues with how CompositorFrameAcks and back
pressure are used in the Renderer, this was a regression on other
platforms.

So removing it.

Bug: 40250049
Change-Id: I3382b6a62536328c636ff398106916b9299c2f9f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6417183
Reviewed-by: Kyle Charbonneau <kylechar@chromium.org>
Commit-Queue: Jonathan Ross <jonross@chromium.org>
Reviewed-by: Bo Liu <boliu@chromium.org>
Reviewed-by: Dominic Farolino <dom@chromium.org>
Reviewed-by: Brian Sheedy <bsheedy@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1444280}