Adding restriction about partial DNS setup.

Author: Oxyjun

src/content/docs/r2/buckets/public-buckets.mdx

@@ -68,7 +68,10 @@ If the zone is on an Enterprise plan, make sure that you [release the zone hold]
 
 ### Restrictions
 
-There is a restriction when using custom domains to access R2 buckets. The domain being used must have been added as a [zone](/fundamentals/setup/accounts-and-zones/#zones) in the same account as the R2 bucket.
+There are restrictions when using custom domains to access R2 buckets.
+
+- The domain being used must have been added as a [zone](/fundamentals/setup/accounts-and-zones/#zones) in the same account as the R2 bucket.
+- The zone containing an R2 Custom Domain must not use a `partial` DNS setup.
 
 ## Disable domain access