Add 'static bound to waker_ref #2525

Job	Run time
cargo test (ubuntu-latest)	3m 4s
cargo test (macos-latest)	6m 12s
cargo test (windows-latest)	4m 40s
cargo +1.36 build (futures-{core, io, sink})	1m 1s
cargo test (ubuntu-latest, aarch64-unknown-linux-gnu)	3m 16s
cargo bench	54s
cargo +stable build	48s
cargo test (ubuntu-latest, armv7-unknown-linux-gnueabihf)	6m 17s
cargo +beta build	43s
cargo test (ubuntu-latest, armv5te-unknown-linux-gnueabi)	6m 28s
cargo hack check --feature-powerset	2m 26s
cargo minimal-versions build	30s
cargo +nightly build	41s
cargo test (ubuntu-latest, i686-unknown-linux-gnu)	3m 49s
cargo miri test	8m 1s
cargo build --target thumbv7m-none-eabi	27s
cargo +1.56 build	2m 54s
cargo build --target thumbv6m-none-eabi	25s
cargo clippy	26s
cargo doc	19s
cargo fmt	6s
cargo test -Z sanitizer=address	4m 48s
cargo test -Z sanitizer=memory	4m 1s
cargo test -Z sanitizer=thread	2m 43s
	1h 4m 59s

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