mgm

Bump `cipher` to `0.5.0-pre.4` #742

Job	Run time
build (1.56.0, thumbv7em-none-eabi)	59s
test (1.56.0)	1m 13s
build (1.56.0, wasm32-unknown-unknown)	58s
test (stable)	33s
build (stable, thumbv7em-none-eabi)	47s
build (stable, wasm32-unknown-unknown)	17s
	4m 47s

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