Update doc example of actix middleware

[tumbl3w33d]

Hi,

since v2 this middleware documentation example won't compile anymore due to lack of Req type declaration: https://actix.rs/docs/middleware/

I've been fiddling around with it to make my middleware compatible, but couldn't figure this one out:

impl<S, B> Transform<S, B> for MyMiddleware
where
    S: Service<Request = ServiceRequest, Response = ServiceResponse<B>, Error = Error>,
    S::Future: 'static,
    B: 'static,
{

the compiler complains about
S: Service<Request = ServiceRequest, Response = ServiceResponse<B>, Error = Error>,
because

wrong number of type arguments: expected 1, found 0
expected 1 type argument

[fakeshadow]

It should be noted that actix-service 2 does not compat with actix-web v3. So this is not an issue for now as website would not migrate to actix-web v4 until it's stable.

If you are using betas you want to look into change log and crate level docs.

[tumbl3w33d]

Thanks for transferring my issue and the info about web v3 not being compatible. I'm not using beta releases, but I only got the web major version pinned and my other dependencies rolling (*). I realized now that you told me, that I should probably look at web's toml to find out about compatible versions.