Update configure-dns.md

[conorbauer23]

Noting that TXT records must be added in order to add a domain, before being able to point A/AAAA records, reported in community slack.

Closes #

Summary

Configure DNS and Provision HTTPS - Small addition to this page to point out that TXT records are required before A/AAAA records can be added to DNS provider.

Post Launch

Do not remove - To be completed by the docs team upon merge:

• [ ] Redirect /old-path/ => /new-path/ (if applicable)
• [ ] Include/exclude pages ^ respectively within docs search service provider (if applicable)