chore: remove h2 from dependencies when http2 feature is off #4444

Job	Run time
cargo-hack	2m 58s
check	39s
check-docs	25s
cargo-public-api-crates (axum)	31s
cargo-deny check (advisories)	24s
dependencies-are-sorted	17s
cargo-public-api-crates (axum-core)	22s
cargo-deny check (bans licenses sources)	24s
cargo-public-api-crates (axum-extra)	29s
cargo-public-api-crates (axum-macros)	15s
Spell Check with Typos	7s
test-nightly	1m 33s
test-versions (stable)	1m 18s
test-docs	1m 35s
test-versions (beta)	1m 15s
armv5te-unknown-linux-musleabi	40s
test-msrv	2m 17s
wasm32-unknown-unknown	14s
	15m 43s

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