Fix broken link in `CopyBufAbortable` docs #2424

Job	Run time
cargo bench	46s
cargo +stable build	37s
cargo clippy	28s
cargo +1.36 build (futures-{core, io, sink})	1m 1s
cargo +beta build	43s
cargo doc	17s
cargo +nightly build	42s
cargo hack check --feature-powerset	2m 42s
cargo fmt	11s
cargo minimal-versions build	30s
cargo miri test	8m 33s
cargo build --target thumbv7m-none-eabi	26s
cargo test -Z sanitizer=address	5m 30s
cargo test (ubuntu-latest)	3m 10s
cargo test -Z sanitizer=memory	4m 4s
cargo +1.56 build	1m 2s
cargo test (macos-latest)	5m 38s
cargo test -Z sanitizer=thread	2m 45s
cargo build --target thumbv6m-none-eabi	26s
cargo test (windows-latest)	4m 49s
cargo test (ubuntu-latest, aarch64-unknown-linux-gnu)	3m 18s
cargo test (ubuntu-latest, armv7-unknown-linux-gnueabihf)	6m 15s
cargo test (ubuntu-latest, armv5te-unknown-linux-gnueabi)	6m 53s
cargo test (ubuntu-latest, i686-unknown-linux-gnu)	3m 36s
	1h 4m 22s

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