remove once_cell from jwt example #4991

Job	Run time
check	2m 25s
cargo-public-api-crates (axum)	29s
cargo-public-api-crates (axum-core)	17s
cargo-hack	5m 59s
cargo-public-api-crates (axum-extra)	26s
cargo-public-api-crates (axum-macros)	17s
check-docs	38s
cargo-deny check (advisories)	23s
dependencies-are-sorted	37s
cargo-deny check (bans licenses sources)	34s
Spell Check with Typos	6s
test-msrv	2m 26s
test-nightly	1m 34s
test-docs	1m 41s
armv5te-unknown-linux-musleabi	47s
test-versions (stable)	3m 3s
wasm32-unknown-unknown	20s
test-versions (beta)	4m 3s
	26m 5s

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