Replace/Update `Errors` example from `failure` to `thiserror`/`anyhow`

[CinchBlue]

Hi,

The failure crate is deprecated. We should try to update our examples to thiserror/anyhow since they are now considered more "idiomatic."

I'd be willing to do the legwork, but I need to have someone validate the example I would write.

Thanks.

[JohnTitor]

AFAIK this repository doesn't contain any example with failure crate. Do you mean actix/examples repo? Then yes, we could replace it with the alternative crate such as thiserror/anyhow. Anyway, I'm going to close this issue as we shouldn't track this here.