LibWeb: Don't call load_src after process_the_iframe_attributes

process_the_iframe_attributes already causes a navigation, so this
would cause a double navigation and blow away any setup that JS may
have done from events fired in process_the_iframe_attributes.

Userland/Libraries/LibWeb/HTML/HTMLIFrameElement.cpp

@@ -48,7 +48,6 @@ void HTMLIFrameElement::inserted()
 
         // 3. Process the iframe attributes for element, with initialInsertion set to true.
         process_the_iframe_attributes(true);
-        load_src(attribute(HTML::AttributeNames::src));
     }
 }