Remove dead dependencies

src/main/java/ch/hepia/Main.java

@@ -5,8 +5,6 @@ import javafx.geometry.Pos;
 import javafx.scene.Scene;
 import javafx.scene.control.Button;
 import javafx.scene.control.Label;
-import javafx.scene.layout.Pane;
-import javafx.scene.layout.StackPane;
 import javafx.scene.layout.VBox;
 import javafx.stage.Stage;