LibJS: Rename GlobalObject::initialize() => initialize_global_object()

This function was shadowing Object::initialize() which cannot be called
on global objects and has a different set of parameters.

Userland/Libraries/LibJS/Runtime/GlobalObject.cpp

@@ -82,7 +82,7 @@ GlobalObject::GlobalObject()
 {
 }
 
-void GlobalObject::initialize()
+void GlobalObject::initialize_global_object()
 {
     auto& vm = this->vm();