docs: Fix authentication / authorization mixup (#8930)

`IsAuthenticatedOrReadOnly` authorizes users that are not
authenticated for read-only access to resources.

Therefore, they are unauthenticated users, not unauthorized users.

Author: cfra

docs/api-guide/permissions.md

@@ -165,7 +165,7 @@ This permission is suitable if you want your API to only be accessible to a subs
 
 ## IsAuthenticatedOrReadOnly
 
-The `IsAuthenticatedOrReadOnly` will allow authenticated users to perform any request.  Requests for unauthorized users will only be permitted if the request method is one of the "safe" methods; `GET`, `HEAD` or `OPTIONS`.
+The `IsAuthenticatedOrReadOnly` will allow authenticated users to perform any request.  Requests for unauthenticated users will only be permitted if the request method is one of the "safe" methods; `GET`, `HEAD` or `OPTIONS`.
 
 This permission is suitable if you want to your API to allow read permissions to anonymous users, and only allow write permissions to authenticated users.