Update CHANGELOG-3.2 for #11271
Update CHANGELOG-3.2 for #11271

Add changelog for etcd_cluster_version metrics from ##11271
cockroachdb/etcd,mkumatag/etcd,mkumatag/etcd,etcd-io/etcd,cockroachdb/etcd,etcd-io/etcd,etcd-io/etcd,li-ang/etcd,mqliang/etcd,coreos/etcd,ajityagaty/etcd,gyuho/etcd,li-ang/etcd,gyuho/etcd,dannysauer/etcd,mqliang/etcd,ajityagaty/etcd,coreos/etcd,rnaveiras/etcd,mqliang/etcd,ajityagaty/etcd,rnaveiras/etcd,dannysauer/etcd,mkumatag/etcd,rnaveiras/etcd