MAINTAINERS: update import path to "go.etcd.io"
MAINTAINERS: update import path to "go.etcd.io"

Signed-off-by: Gyuho Lee <0fbd30d364d71722b926950b451cecd97b54fc29@amazon.com>

ajityagaty/etcd,li-ang/etcd,xiang90/etcd,mqliang/etcd,gyuho/etcd,mqliang/etcd,xiang90/etcd,cockroachdb/etcd,coreos/etcd,etcd-io/etcd,cockroachdb/etcd,dannysauer/etcd,mkumatag/etcd,gyuho/etcd,ajityagaty/etcd,joshix/etcd,etcd-io/etcd,dannysauer/etcd,mqliang/etcd,mkumatag/etcd,ajityagaty/etcd,etcd-io/etcd,vimalk78/etcd,rnaveiras/etcd,coreos/etcd,rnaveiras/etcd,vimalk78/etcd,mkumatag/etcd,rnaveiras/etcd,joshix/etcd,li-ang/etcd