Update utils.py

This works with every combination of VHM (including _vh_, using mysite.com/Plone/ as public address) and with navigation root. This is a minimal change that fix the relative path. This function is used in https://github.com/plone/plone.restapi/blob/main/src/plone/restapi/serializer/dxfields.py too

For the discussion, see #710

plone/app/contenttypes/utils.py

@@ -48,7 +48,7 @@ def replace_link_variables_by_paths(context, url):
 
 
 def _replace_variable_by_path(url, variable, obj):
-    path = "/".join(obj.getPhysicalPath())
+    path = obj.absolute_url_path()
     return url.replace(variable, path)