net: fix ExampleUDPConn_WriteTo

Change-Id: I174b17395509d4c9fb55332c2405890b2a350cbd
Reviewed-on: https://go-review.googlesource.com/115218
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/net/example_test.go

@@ -128,7 +128,7 @@ func ExampleUDPConn_WriteTo() {
 	}
 	defer conn.Close()
 
-	dst, err := net.ResolveIPAddr("udp", "192.0.2.1:2000")
+	dst, err := net.ResolveUDPAddr("udp", "192.0.2.1:2000")
 	if err != nil {
 		log.Fatal(err)
 	}