Resolve clippy::unnecessary_map_or warning (#2904) #2992

Job	Run time
cargo +1.36 build (futures-{core, io, sink})	39s
cargo test (ubuntu-latest)	2m 38s
cargo test (macos-latest)	6m 3s
cargo bench	53s
cargo +stable build	39s
cargo test (windows-latest)	4m 26s
cargo hack check --feature-powerset	2m 29s
cargo +beta build	37s
cargo test (ubuntu-latest, aarch64-unknown-linux-gnu)	3m 21s
cargo minimal-versions build	23s
cargo +nightly build	37s
cargo test (ubuntu-latest, armv7-unknown-linux-gnueabihf)	6m 11s
cargo miri test	13m 56s
cargo test (ubuntu-latest, armv5te-unknown-linux-gnueabi)	6m 27s
cargo test (ubuntu-latest, i686-unknown-linux-gnu)	3m 30s
cargo build --target thumbv7m-none-eabi	26s
cargo +1.63 build	1m 8s
cargo build --target thumbv6m-none-eabi	25s
cargo clippy	17s
cargo doc	19s
cargo fmt	15s
cargo test -Z sanitizer=address	3m 28s
cargo test -Z sanitizer=memory	5m 34s
cargo test -Z sanitizer=thread	2m 28s
	1h 7m 9s

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