remove pin as pin! not stable for current toolchain #4383

Job	Run time
cargo-public-api-crates (axum)	1m 2s
cargo-hack	6m 4s
cargo-public-api-crates (axum-core)	47s
check-docs	37s
check	2m 9s
cargo-public-api-crates (axum-extra)	56s
cargo-deny check (advisories)	14s
cargo-public-api-crates (axum-macros)	51s
dependencies-are-sorted	45s
cargo-deny check (bans licenses sources)	18s
Spell Check with Typos	0s
test-msrv	6m 28s
test-versions (stable)	3m 56s
test-versions (beta)	4m 2s
test-docs	2m 16s
armv5te-unknown-linux-musleabi	1m 13s
test-nightly	2m 26s
wasm32-unknown-unknown	25s
	34m 29s

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