LibWeb: Never claim "rendering opportunity" for SVG-as-image documents

Since we drive painting for SVG-as-image manually anyway, there's no
need for them to say they are "ready to paint", since that just causes
unnecessary extra processing in the HTML event loop.

Userland/Libraries/LibWeb/SVG/SVGDecodedImageData.cpp

@@ -49,7 +49,7 @@ public:
     virtual void request_file(FileRequest) override { }
     virtual void paint(DevicePixelRect const&, Gfx::Bitmap&, Web::PaintOptions = {}) override { }
     virtual void schedule_repaint() override { }
-    virtual bool is_ready_to_paint() const override { return true; }
+    virtual bool is_ready_to_paint() const override { return false; }
 
 private:
     explicit SVGPageClient(Page& host_page)