[R2] Clarifying wording on adding domain as a zone (#21748)

* Clarifying wording on adding domain as a zone.

* Linking the word Zone to the relevant page.

Author: Oxyjun

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

@@ -68,7 +68,7 @@ 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 belong to the same account as the R2 bucket.
+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.
 
 ## Disable domain access