Revert "enable libaom"

This reverts commit 80428a9587801289b331674365fc09523319288c.

AV1 is not ready. Disable it on the M69 branch.

BUG=838380,866522

Change-Id: I5fcad78ded0f9e03a44b7def5fee5becd6a4cbf9
Reviewed-on: https://chromium-review.googlesource.com/1146982
Reviewed-by: Johann Koenig <johannkoenig@google.com>
Cr-Commit-Position: refs/branch-heads/3497@{#780}
Cr-Branched-From: 271eaf50594eb818c9295dc78d364aea18c82ea8-refs/heads/master@{#576753}
1 file changed