signature: bump `hex-literal` to v0.4 #1784

Job	Run time
minimal-versions	51s
build (1.65.0, thumbv7em-none-eabi)	5m 13s
test (1.65.0)	5m 18s
build (1.65.0, wasm32-unknown-unknown)	5m 14s
test (stable)	25s
build (stable, thumbv7em-none-eabi)	14s
build (stable, wasm32-unknown-unknown)	13s
	17m 28s

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