Fix readme

Author: leg100

readme.md

@@ -29,7 +29,7 @@ func main() {
 
 	// Create a signed URL that expires in one hour.
 	signed, _ := signer.Sign("https://example.com/a/b/c?foo=bar", time.Hour)
-	fmt.Println("signed url:", signed)
+	fmt.Println(signed)
 	// Outputs something like:
 	// https://example.com/a/b/c?expiry=1667331055&foo=bar&signature=TGvxmRwpoAUt9YEIbeJ164lMYrzA2DBnYB9Lcy9m1T