Some code simplifications

1. `number_width` isn't used later
2. `return_type` is used only once
3. AudioServer::get_singleton()->get_channel_count() always returns a channel_count of 1 or larger
4. negative `aa->backward` conditional
5. `current_canvas` == `find_world_2d()->get_canvas()`
6. identical if `render_shadows`

servers/rendering/renderer_rd/forward_mobile/render_forward_mobile.cpp

@@ -593,12 +593,10 @@ void RenderForwardMobile::_pre_opaque_render(RenderDataRD *p_render_data) {
 
 	bool render_shadows = p_render_data->directional_shadows.size() || p_render_data->shadows.size();
 
-	if (render_shadows) {
-		RENDER_TIMESTAMP("Render Shadows");
-	}
-
 	//prepare shadow rendering
 	if (render_shadows) {
+		RENDER_TIMESTAMP("Render Shadows");
+
 		_render_shadow_begin();
 
 		//render directional shadows