Remove outdated statement on secondary-primary conversion

Author: RebeccaTamachiro

src/content/docs/dns/zone-setups/zone-transfers/cloudflare-as-secondary/index.mdx

@@ -26,7 +26,3 @@ B & C <--DNS lookups--> D[Resolver] <--DNS lookups--> E((User))
 ## Availability
 
 Secondary DNS is only available to Enterprise customers. For more details on activation and pricing, contact your account team.
-
-## Limitations
-
-At this time, you cannot convert a secondary zone to a primary zone.