Remove an outdated comment from docs (#2774) #2284

Job	Run time
cargo clippy	34s
cargo bench	1m 23s
cargo +stable build	1m 10s
codegen	35s
cargo +beta build	1m 5s
cargo doc	29s
cargo +1.36 build (futures-{core, io, sink})	2m 49s
cargo +nightly build	1m 24s
cargo hack check --feature-powerset	3m 25s
cargo fmt	21s
cargo minimal-versions build	45s
cargo miri test	9m 2s
cargo build --target thumbv7m-none-eabi	42s
cargo build --target thumbv6m-none-eabi	55s
cargo test -Z sanitizer=address	5m 14s
cargo test (ubuntu-latest)	4m 4s
cargo test -Z sanitizer=memory	3m 40s
cargo +1.56 build	2m 3s
cargo test (macos-latest)	7m 56s
cargo test -Z sanitizer=thread	4m 13s
cargo test (windows-latest)	8m 44s
cargo test (ubuntu-latest, aarch64-unknown-linux-gnu)	6m 5s
cargo test (ubuntu-latest, armv7-unknown-linux-gnueabihf)	8m 8s
cargo test (ubuntu-latest, armv5te-unknown-linux-gnueabi)	10m 39s
cargo test (ubuntu-latest, i686-unknown-linux-gnu)	4m 33s
	1h 29m 58s

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