femtovg: fix warning about unused variable

The layer_origin should normally always be 0,0 for the Clip element
since the Clip element always cover its parent.
But the correct thing to do is anyway to translate by the origin.

Author: ogoffart

internal/renderers/femtovg/itemrenderer.rs

@@ -690,7 +690,10 @@ impl<'a, R: femtovg::Renderer + TextureImporter> ItemRenderer for GLItemRenderer
                     self.scale_factor,
                 );
 
-                self.canvas.borrow_mut().fill_path(&layer_path, &layer_image_paint);
+                self.canvas.borrow_mut().save_with(|canvas| {
+                    canvas.translate(layer_origin.x, layer_origin.y);
+                    canvas.fill_path(&layer_path, &layer_image_paint);
+                });
             }
 
             RenderingResult::ContinueRenderingWithoutChildren