Windows: repaint entire Overlay Frame instead of only root pane

Commonalize repainting of the Overlay with how the OSK is repainted (see
previous commit)

src/main/java/de/bwravencl/controllerbuddy/gui/Main.java

@@ -2425,9 +2425,8 @@ private void repaintOnScreenKeyboardAndOverlay() {
 		}
 
 		if (isWindows && overlayFrame != null) {
-			final var overlayFrameContentPane = overlayFrame.getContentPane();
-			overlayFrameContentPane.validate();
-			overlayFrameContentPane.repaint();
+			overlayFrame.validate();
+			overlayFrame.repaint();
 		}
 	}