Fix comment in testing example #4082

Job	Run time
check	48s
cargo-hack	3m 7s
cargo-public-api-crates (axum)	35s
check-docs	27s
cargo-public-api-crates (axum-core)	18s
dependencies-are-sorted	14s
cargo-public-api-crates (axum-extra)	30s
cargo-deny check (advisories)	25s
Spell Check with Typos	5s
cargo-public-api-crates (axum-macros)	15s
cargo-deny check (bans licenses sources)	26s
test-nightly	1m 37s
test-msrv	1m 20s
armv5te-unknown-linux-musleabi	37s
test-docs	1m 47s
test-versions (stable)	2m 30s
wasm32-unknown-unknown	24s
test-versions (beta)	2m 7s
	17m 32s

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