fix: error[E0658]: attribute name space is experimental #4501

Job	Run time
check	48s
cargo-hack	28s
cargo-public-api-crates (axum)	59s
check-docs	48s
cargo-public-api-crates (axum-core)	49s
dependencies-are-sorted	44s
cargo-public-api-crates (axum-extra)	56s
cargo-deny check (advisories)	26s
cargo-public-api-crates (axum-macros)	45s
cargo-deny check (bans licenses sources)	26s
Spell Check with Typos	7s
test-msrv	0s
test-nightly	0s
test-docs	0s
armv5te-unknown-linux-musleabi	0s
test-versions	0s
wasm32-unknown-unknown	0s
	7m 16s

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