Shared: fix shared futures missing wake up #2922

Job	Run time
cargo clippy	15s
cargo +1.36 build (futures-{core, io, sink})	55s
cargo bench	50s
cargo +stable build	39s
cargo doc	18s
cargo +beta build	40s
cargo hack check --feature-powerset	2m 17s
cargo fmt	5s
cargo +nightly build	39s
cargo minimal-versions build	24s
cargo miri test	2m 17s
cargo build --target thumbv7m-none-eabi	29s
cargo build --target thumbv6m-none-eabi	28s
cargo test -Z sanitizer=address	2m 15s
cargo test (ubuntu-latest)	2m 14s
cargo +1.56 build	1m 27s
cargo test -Z sanitizer=memory	2m 16s
cargo test (macos-latest)	2m 16s
cargo test -Z sanitizer=thread	2m 15s
cargo test (windows-latest)	2m 10s
cargo test (ubuntu-latest, aarch64-unknown-linux-gnu)	2m 16s
cargo test (ubuntu-latest, armv7-unknown-linux-gnueabihf)	2m 15s
cargo test (ubuntu-latest, armv5te-unknown-linux-gnueabi)	2m 16s
cargo test (ubuntu-latest, i686-unknown-linux-gnu)	2m 16s
	34m 12s

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