fix: remove deprecated url.parse() from custom-server example (#96105)
Fixes #86951
Removes the deprecated legacy `url.parse()` API (DEP0169) from the
custom-server example. The `parsedUrl` parameter is optional, so the
simplest fix is to remove the `parse()` call and pass only `(req, res)`
to the handler, matching the docs code block that was already updated in
#86986.