LibJS: Remove ProxyPrototype

Proxy is an "exotic object" and doesn't have its own prototype. Use the
regular object prototype instead, but most stuff is happening on the
target object anyway. :^)

Libraries/LibJS/Runtime/ProxyConstructor.cpp

@@ -41,7 +41,6 @@ void ProxyConstructor::initialize(GlobalObject& global_object)
 {
     auto& vm = this->vm();
     NativeFunction::initialize(global_object);
-    define_property(vm.names.prototype, global_object.proxy_prototype(), 0);
     define_property(vm.names.length, Value(2), Attribute::Configurable);
 }