Hi,
For a web app it is preferred (not mandatory) to leave the txt record in place to prevent potential future subdomain takeover. For static web app it makes no difference--in other words you can delete it if you want.
Excerpt from documentation:
These records don't prevent someone from creating the Azure App Service with the same name that's in your CNAME entry. Without the ability to prove ownership of the domain name, threat actors can't receive traffic or control the content.
Above warning from this article.
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Thanks.
-TP