Upgrade tokio-tungstenite to 0.21 #4172

Job	Run time
check-docs	20s
cargo-hack	2m 55s
cargo-public-api-crates (axum)	31s
check	45s
cargo-public-api-crates (axum-core)	18s
cargo-deny check (advisories)	27s
cargo-public-api-crates (axum-extra)	29s
dependencies-are-sorted	17s
cargo-deny check (bans licenses sources)	21s
cargo-public-api-crates (axum-macros)	16s
Spell Check with Typos	5s
test-docs	1m 41s
test-nightly	1m 30s
test-msrv	2m 10s
armv5te-unknown-linux-musleabi	22s
test-versions (stable)	2m 9s
wasm32-unknown-unknown	20s
test-versions (beta)	1m 49s
	16m 45s

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