bcrypt-pbkdf: scrypt: bump cipher to `0.5.0-pre.4` #876

Job	Run time
build (1.72.0, thumbv7em-none-eabi)	16s
build (1.72.0, wasm32-unknown-unknown)	31s
minimal-versions	0s
build (stable, thumbv7em-none-eabi)	56s
test (1.72.0)	19s
build (stable, wasm32-unknown-unknown)	11s
test (stable)	12s
	2m 25s

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