Update setup.mdx

Added a note to mention Partial set ups are not supported on Cloudflare Registrar domains

Author: sarah-adam

src/content/docs/dns/zone-setups/partial-setup/setup.mdx

@@ -14,6 +14,7 @@ import { Details, Render, GlossaryTooltip, Steps } from "~/components";
 
 :::note
 A partial setup is only available to customers on a Business or Enterprise plan.
+Partial setups are not supported on Cloudflare Registrar domains.
 :::
 
 ---