removed unused runtime properties

src/main/java/cz/kamma/jkeepass/KeepassApp.java

@@ -90,12 +90,6 @@ public class KeepassApp extends JFrame {
     private TrayIcon trayIcon;
 
     public KeepassApp() {
-        // Set properties before anything else
-        System.setProperty("sun.awt.enableExtraMouseButtons", "true");
-        // Force GTK 2 or 3 for better X11 integration in Cinnamon
-        System.setProperty("jdk.gtk.version", "3");
-        // Ensure we don't use the old way of drawing that can conflict with XApp
-        System.setProperty("sun.java2d.xrender", "true");
 
         setTitle("JKeepass");
         setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);