update modelclone with django 4.0 compatible

[Subhrans]

In django 4.0 some functions has been removed permanently. One of the major function is removed that must effect in this package (django-modelclone). that function is URL which was present in from django.conf.urls import url.

Here my suggestion is to replace url() with re_path() function.
re_path present in from django.urls import re_path

[gregorybrooks]

I am hitting this problem as well. Do you plan to get modelclone working with Django 4?