audit: update the mailing list in MAINTAINERS

audit: update the mailing list in MAINTAINERS

We've moved the upstream Linux Kernel audit subsystem discussions to
a new mailing list, this patch updates the MAINTAINERS info with the
new list address.

Marking this for stable inclusion to help speed uptake of the new
list across all of the supported kernel releases.  This is a doc only
patch so the risk should be close to nil.

Cc: stable@vger.kernel.org
Signed-off-by: Paul Moore <paul@paul-moore.com>