[a11y] Remove AutoDisableAccessibility from fieldtrial testing config

Change-Id: I37d9799d58737709781e728d78e4f6931804cf9a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7831241
Reviewed-by: Greg Thompson <grt@chromium.org>
Commit-Queue: Lucas Radaelli <lucasradaelli@google.com>
Cr-Commit-Position: refs/heads/main@{#1627656}
NOKEYCHECK=True
GitOrigin-RevId: 164af23bf4d999036c7181124f9f2ad1c1984b0d