fix typo in examples README: plural form examples #3866

Job	Run time
cargo-hack	9m 22s
check	3m 19s
check-docs	1m 9s
cargo-public-api-crates (axum)	1m 29s
cargo-public-api-crates (axum-core)	1m 12s
cargo-public-api-crates (axum-extra)	1m 29s
cargo-public-api-crates (axum-macros)	1m 4s
cargo-deny check (advisories)	33s
cargo-deny check (bans licenses sources)	38s
dependencies-are-sorted	1m 19s
Spell Check with Typos	5s
test-docs	5m 0s
test-msrv	8m 8s
test-versions (stable)	6m 53s
test-versions (beta)	9m 15s
armv5te-unknown-linux-musleabi	2m 14s
test-nightly	3m 38s
wasm32-unknown-unknown	1m 4s
	57m 51s

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