MAINTAINERS: change gyuho's email to AWS
MAINTAINERS: change gyuho's email to AWS

Signed-off-by: Gyuho Lee <3454051ee3341eb69bdf6fca40899cdad4d86496@gmail.com>

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