add new google-build-admins to release-managers@
add new google-build-admins to release-managers@

see: https://github.com/kubernetes/sig-release/issues/1150
thockin/k8s.io,kubernetes/k8s.io,kubernetes/k8s.io,kubernetes/k8s.io,thockin/k8s.io,kubernetes/k8s.io,thockin/k8s.io,thockin/k8s.io