DO NOT MERGE: untrusted_app: drop /proc auditallow

It's unlikely we'll get /proc locked down for the N release, so
delete the auditallow to avoid spamming the logs. Mark this
commit as DO NOT MERGE so we can continue to make progress on this
for future Android releases.

Change-Id: Ibf27bc5cb1b23c21e123aae8a4f190560d0ac2dc