rpc: fix typo in documentation client example

The example incorrectly dereferenced an integer variable

R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/5129041

src/pkg/rpc/server.go

@@ -97,7 +97,7 @@
 		if err != nil {
 			log.Fatal("arith error:", err)
 		}
-		fmt.Printf("Arith: %d*%d=%d", args.A, args.B, *reply)
+		fmt.Printf("Arith: %d*%d=%d", args.A, args.B, reply)
 
 	or