synchronized void uninstall() {
			if( rendererComponent == null )
				return;

			rendererComponent.putClientProperty( KEY_MAC_STYLE_HINT, null );

			if( rendererComponent.getBorder() == this )
				rendererComponent.setBorder( rendererBorder );
			rendererComponent = null;
			rendererBorder = null;
		}
Uninstall border from previously installed component.
Because this border is installed in PopupListCellRenderer.getListCellRendererComponent(),
there is no single place to uninstall it.
This is the reason why this method is called from various places.
flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatComboBoxUI.java