Don't recommend async-redis-session as it is effectively dead

[Elizafox]

Hello,

As the title says, async-redis-session is effectively dead, but it's recommended in the readme. There hasn't been activity on the repo since 2021, and not much heard from the author since 2022. The crate doesn't build on modern rust, and doesn't work with modern Redis.

It may be better to recommend https://github.com/brkp/async-fred-session instead? It isn't ideal either, fred has a sluggish upstream too, but it does work.

[maxcountryman]

I'd be interested in helping to maintain a fork of both async-redis-session and async-sqlx-session (the latter of which I have a fork I'm intending to use with axum-sessions).

Ultimately I think there's a bigger question about the future of this crate and perhaps there's a need for a fork of this and the subsequent session crates.