Upgrade tokio-tungstenite to 0.21 #4177

Job	Run time
cargo-hack	2m 46s
cargo-public-api-crates (axum)	1m 4s
check-docs	18s
cargo-public-api-crates (axum-core)	50s
check	44s
cargo-public-api-crates (axum-extra)	59s
cargo-deny check (advisories)	24s
cargo-public-api-crates (axum-macros)	49s
cargo-deny check (bans licenses sources)	24s
dependencies-are-sorted	14s
Spell Check with Typos	4s
test-docs	1m 34s
test-msrv	4m 16s
armv5te-unknown-linux-musleabi	26s
test-nightly	1m 40s
wasm32-unknown-unknown	12s
test-versions (stable)	1m 43s
test-versions (beta)	1m 59s
	20m 26s

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