LibWeb: Move SVGPathElement methods into SVGGeometryElement

From the spec:

> Interface SVGGeometryElement represents SVG elements whose rendering
> is defined by geometry with an equivalent path, and which can be
> filled and stroked. This includes paths and the basic shapes.

- https://svgwg.org/svg2-draft/types.html#InterfaceSVGGeometryElement

Making them all create an SVGPathBox, and return a Path from get_path(),
means we can implement the "basic shapes" using the path system we
already have. :^)

Userland/Libraries/LibWeb/SVG/SVGPathElement.cpp

@@ -443,11 +443,6 @@ SVGPathElement::SVGPathElement(DOM::Document& document, QualifiedName qualified_
 {
 }
 
-RefPtr<Layout::Node> SVGPathElement::create_layout_node(NonnullRefPtr<CSS::StyleProperties> style)
-{
-    return adopt_ref(*new Layout::SVGPathBox(document(), *this, move(style)));
-}
-
 void SVGPathElement::parse_attribute(const FlyString& name, const String& value)
 {
     SVGGeometryElement::parse_attribute(name, value);