Bump `cipher` to `0.5.0-pre.4` #849

Job	Run time
build (1.56.0, armv7a-none-eabi)	3m 30s
build (1.56.0, thumbv7em-none-eabi)	3m 24s
build (1.56.0, wasm32-unknown-unknown)	3m 25s
test (i686-unknown-linux-gnu, 1.56.0, sudo apt update && sudo apt install gcc-multilib)	3m 48s
build (stable, armv7a-none-eabi)	13s
test (i686-unknown-linux-gnu, stable, sudo apt update && sudo apt install gcc-multilib)	40s
test (x86_64-unknown-linux-gnu, 1.56.0)	3m 22s
build (stable, thumbv7em-none-eabi)	9s
test (x86_64-unknown-linux-gnu, stable)	21s
build (stable, wasm32-unknown-unknown)	12s
	19m 4s

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