stream: bump version of async-stream

[loyd]

The tokio-test crate depends on async-stream v0.3.0 that incorrectly specifies its dependencies.

How to reproduce

Firstly, create an empty project with the next dev deps:

[dev-dependencies]
tokio-test = "0.4.2"

Secondly, fetch minimal versions of deps (cargo +nightly update -Zminimal-versions).

Now it fails to compile (cargo test):

error[E0277]: the trait bound `TokenStream2: From<proc_macro2::TokenTree>` is not satisfied
  --> /home/.cargo/registry/src/github.com-1ecc6299db9ec823/async-stream-impl-0.3.0/src/lib.rs:17:36
   |
17 |     let input = TokenStream2::from(TokenTree::Group(Group::new(Delimiter::Brace, input)));
   |                 ------------------ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `From<proc_macro2::TokenTree>` is not implemented for `TokenStream2`
   |                 |
   |                 required by a bound introduced by this call
   |
   = help: the trait `From<proc_macro::TokenStream>` is implemented for `TokenStream2`

It occurs because async-stream v0.3.0 wrongly specifies proc-macro2 = "1" but uses conversion added in v1.0.2.

The latest async-stream doesn't use this conversion, so there is no error.

[Darksonn]

Thanks.