LibWeb/LibJS: Avoid GC visit of raw pointers where possible

This is mostly motivated for aesthetics, but also helps avoid some null
checks when we have a NonnullGCPtr<T> or in some cases a T&.

Userland/Libraries/LibJS/Runtime/ECMAScriptFunctionObject.cpp

@@ -533,7 +533,7 @@ void ECMAScriptFunctionObject::visit_edges(Visitor& visitor)
     m_script_or_module.visit(
         [](Empty) {},
         [&](auto& script_or_module) {
-            visitor.visit(script_or_module.ptr());
+            visitor.visit(script_or_module);
         });
 }