macros: fix rustfmt on 1.48.0 (#3160)
macros: fix rustfmt on 1.48.0 (#3160)

## Motivation

Looks like the Rust 1.48.0 version of `rustfmt` changed some formatting
rules (fixed some bugs?), and some of the code in `tokio-macros` is no
longer correctly formatted. This is breaking CI.

## Solution

This commit runs rustfmt on Rust 1.48.0. This fixes CI.

Closes #3158
tokio-rs/tokio,tokio-rs/tokio