resources.Teardown() & resources.AssessUpdate() are not implemented

[maximilianbraun]

We currently have two methods which are not implemented and have only been added to complete the API.

https://github.com/crossplane-contrib/xp-testing/blob/main/pkg/resources/resources.go#L344
https://github.com/crossplane-contrib/xp-testing/blob/main/pkg/resources/resources.go#L358

For me its unclear if they're needed.

// pointed out by @v0lkc