Bump `cipher` to v0.5.0-pre.6; `digest` to v0.11.0-pre.9 #51

Job	Run time
build (1.71.0, thumbv7em-none-eabi)	17s
build (1.71.0, wasm32-unknown-unknown)	15s
build (stable, thumbv7em-none-eabi)	14s
minimal-versions	0s
test (1.71.0)	18s
build (stable, wasm32-unknown-unknown)	14s
test (stable)	15s
	1m 33s

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