documentation: updated grpc documentation
documentation: updated grpc documentation

I noticed that the docs mention the grpc proxy will listen on port 8080,
but the above example is explicitly telling it to listen on 2379.
Removing confusion.

mkumatag/etcd,mqliang/etcd,lorneli/etcd,li-ang/etcd,sinsharat/etcd,etcd-io/etcd,glevand/coreos--etcd,etcd-io/etcd,mqliang/etcd,gyuho/etcd,ajityagaty/etcd,gyuho/etcd,mkumatag/etcd,joshix/etcd,ajityagaty/etcd,cockroachdb/etcd,bdarnell/etcd,cockroachdb/etcd,sinsharat/etcd,mqliang/etcd,coreos/etcd,ajityagaty/etcd,bdarnell/etcd,mkumatag/etcd,rnaveiras/etcd,xiang90/etcd,sebrandon1/etcd,vimalk78/etcd,rnaveiras/etcd,lorneli/etcd,xiang90/etcd,rnaveiras/etcd,sebrandon1/etcd,dannysauer/etcd,fanminshi/etcd,etcd-io/etcd,fanminshi/etcd,vimalk78/etcd,glevand/coreos--etcd,joshix/etcd,dannysauer/etcd,li-ang/etcd,coreos/etcd