Remove unnecessary brackets in chat example

[srcres258]

Motivation

Usage examples of the tokio::select macro mentioned in tokio's documentation indicate that brackets are redundant when writing the macro branches.

e.g. It's more preferred to write

    let next = tokio::select! {
        v = stream1.next() => v.unwrap(),
        v = stream2.next() => v.unwrap(),
    };

than

    let next = tokio::select! {
        v = (stream1.next()) => v.unwrap(),
        v = (stream2.next()) => v.unwrap(),
    };

Solution

Remove the unnecessary brackets in chat example code.

[jplatte]

Thanks!