Rename Part.URL -> part.link

- Previous migration needed some tweaking to get it to run... because.. why?
- It seems to pass when running manage.py migrate but fails when running manage.py test
- Stumped on this one

InvenTree/part/views.py

@@ -1388,8 +1388,6 @@ class BomExport(AjaxView):
         url += '?file_format=' + fmt
         url += '&cascade=' + str(cascade)
 
-        print("URL:", url)
-
         data = {
             'form_valid': part is not None,
             'url': url,