Update dns-record-types.mdx

[vianaedson]

SOA records require an Account Entitlement for ENT customers, not enabled by default: Authoritative DNS - Custom SOA Record Allowed, so customers may need to reach out to support or their account teams to enable it

Summary

Customer in ticket 01217536 tried to edit RNAME in SOA and got errors. Troubleshooting it led to find that this entitlement needed to be enabled, but neither the customer or the owner TSE knew about it

Screenshots (optional)

Documentation checklist

• The documentation style guide has been adhered to.
• If a larger change - such as adding a new page- an issue has been opened in relation to any incorrect or out of date information that this PR fixes.
• Files which have changed name or location have been allocated redirects.

[RebeccaTamachiro]

Not merging yet, while I check the expected behavior with the team.

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