gui2/tcustom_tod: Remove direct call to gui2::twindow::draw()

It's unnecessary, results in a noticeable performance penality when
updating ToD color shift sliders, and the documentation says it's not to
be called directly (which raises the question of why it's a public
method in the first place).

src/gui/dialogs/editor/custom_tod.cpp

@@ -209,7 +209,6 @@ void tcustom_tod::update_tod_display(twindow& window)
 	display_->draw();
 
 	window.invalidate_layout();
-	window.draw();
 }
 
 void tcustom_tod::update_lawful_bonus(twindow& window)