Remove unused imports

Author: tschie

src/main/java/com/esri/samples/tiledlayers/export_vector_tiles/AuthenticationDialog.java

@@ -24,8 +24,6 @@
 import javafx.scene.control.PasswordField;
 import javafx.scene.control.TextField;
 
-import com.esri.arcgisruntime.security.Credential;
-import com.esri.arcgisruntime.security.OAuthConfiguration;
 import com.esri.arcgisruntime.security.UserCredential;
 
 /**