remove authenticationDialog window owner

Author: tschie

src/main/java/com/esri/samples/portal/oauth/OAuthController.java

@@ -45,7 +45,6 @@ private void initialize() {
   void authenticate() {
 
     AuthenticationDialog authenticationDialog = new AuthenticationDialog();
-    authenticationDialog.initOwner(fullName.getScene().getWindow());
     authenticationDialog.show();
     authenticationDialog.setOnCloseRequest(r -> {