net/http/httputil: fix typo in comment.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/6272050

src/pkg/net/http/httputil/dump.go

@@ -75,7 +75,7 @@ func DumpRequestOut(req *http.Request, body bool) ([]byte, error) {
 
 	// Use the actual Transport code to record what we would send
 	// on the wire, but not using TCP.  Use a Transport with a
-	// customer dialer that returns a fake net.Conn that waits
+	// custom dialer that returns a fake net.Conn that waits
 	// for the full input (and recording it), and then responds
 	// with a dummy response.
 	var buf bytes.Buffer // records the output