Dead guides link in Cognito extension

[holly-cummins]

The quarkus-extension.yaml for io.quarkiverse.amazonservices:quarkus-amazon-cognito-user-pools points to a guide at https://quarkus.io/guides/amazon-cognitouserpools, but this page does not exist.

I haven't created a PR since I'm not sure if it's better to create a guide page or remove the guides line in the extension metadata. Probably, even if a guide is created, it would be in the quarkiverse docs rather than the main quarkus guides, so the metadata would need updating in both cases.

See also quarkusio/quarkus#31149, which would update the extension template so that it's harder to end up accidentally publishing extensions with dead guide links.