Disable kZeroCopyDesktopCapture feature flag

This disables the desktop capture zero copy feature flag to act as a
killswitch for a major regression (b/523190052).

A revert of the original feature was attempted but failed with a
merge conflict, so disabling the flag is the safest short-term
mitigation while a fix is developed for Linux and Windows.

Bug: 523190052
Change-Id: Ia02721c2b3bf53d01746dbcae8f5e9f0ae18a22c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7934869
Commit-Queue: Jordan Bayles <jophba@chromium.org>
Reviewed-by: Alexander Cooper <alcooper@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1646328}