Menu: separator menu item doesn't take care of className

[ar2my]

Describe the bug

In a menu model containing separator with className :
{ separator: true, className: 'user-separator-classname' }
the className doesn't applies to final rendering

Reproducer

https://stackblitz.com/edit/ywyjat?file=src%2FApp.jsx,src%2Findex.css

PrimeReact version

10.6.6

React version

17.x

Language

TypeScript

Build / Runtime

Create React App (CRA)

Browser(s)

No response

Steps to reproduce the behavior

1. open reproducer
2. on the right the separator should appear darkgreen 10px height
   inspecting dom: the 'user-separator-classname' doesn't appears as class attribute:
   

Expected behavior

menuitem separator should take care of user's classname.

[ar2my]

proposed PR: #6883