bump `digest`/`cipher` to `0.11.0-pre.8`/`0.5.0-pre.4` #297

Job	Run time
build (1.72.0, thumbv7em-none-eabi)	14s
build (1.72.0, wasm32-unknown-unknown)	18s
build (stable, thumbv7em-none-eabi)	7s
test (1.72.0)	21s
build (stable, wasm32-unknown-unknown)	21s
test (stable)	13s
minimal-versions / minimal-versions	31s
	2m 5s

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