LibWeb: Rename invalidate_layout() => invalidate_layout_tree()

I believe this is slightly less confusing, since what the function does
is trigger a full layout tree *rebuild*, not just a relayout.

Userland/Libraries/LibWeb/SVG/SVGGraphicsElement.cpp

@@ -45,7 +45,7 @@ void SVGGraphicsElement::attribute_changed(FlyString const& name, Optional<Strin
         if (transform_list.has_value())
             m_transform = transform_from_transform_list(*transform_list);
         // FIXME: This should only invalidate the contents of the SVG.
-        document().invalidate_layout();
+        document().invalidate_layout_tree();
     }
 }