Clean maintainer list
Clean maintainer list

Chris, Ildiko, Liusheng, Riota and ZhiQiang did not contribute to Aodh ever or
for a long time. Let's make it clear it's a very small team job now.

Change-Id: I6c65d5c0b4e983364aa3717b1e34396d25d2bd28

openstack/aodh,openstack/aodh