Fix PrivateCookieJar documentation example comments #5067

Job	Run time
check-docs	33s
cargo-hack	6m 15s
cargo-public-api-crates (axum)	29s
check	2m 23s
cargo-public-api-crates (axum-core)	17s
cargo-deny check (advisories)	24s
cargo-public-api-crates (axum-extra)	25s
dependencies-are-sorted	34s
Spell Check with Typos	4s
cargo-deny check (bans licenses sources)	24s
cargo-public-api-crates (axum-macros)	26s
test-nightly	1m 41s
test-msrv	2m 30s
test-docs	1m 49s
armv5te-unknown-linux-musleabi	58s
test-versions (stable)	4m 1s
test-versions (beta)	4m 5s
wasm32-unknown-unknown	23s
	27m 41s

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