test: use reserved .invalid TLD for invalid address in test

RFC 2606 reserves ithe .invalid top-level-domain for use in "domain
names that are sure to be invalid and which it is obvious at a glance
are invalid." Replace `dne.example.com` which actually isn't guaranteed
to not exist. (example.com is for examples, but at least one address
does in fact exist in that TLD.)

PR-URL: https://github.com/nodejs/node/pull/30545


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>