[9.x] Document MinIO limitation with temporaryUrl (#8107)

* Update sail.md

* Update sail.md

Co-authored-by: Taylor Otwell <[email protected]>

Author: driesvints

sail.md

@@ -251,6 +251,9 @@ AWS_URL=http://localhost:9000/local
 
 You may create buckets via the MinIO console, which is available at `http://localhost:8900`. The default username for the MinIO console is `sail` while the default password is `password`.
 
+> **Warning**  
+> Generating temporary storage URLs via the `temporaryUrl` method is not supported when using MinIO.
+
 <a name="running-tests"></a>
 ## Running Tests