scripts/release: fix SHA256SUMS command
scripts/release: fix SHA256SUMS command

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

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