bcrypt-pbkdf: scrypt: bump cipher to `0.5.0-pre.4` #815

Job	Run time
build (1.72.0, thumbv7em-none-eabi)	21s
build (1.72.0, wasm32-unknown-unknown)	20s
build (stable, thumbv7em-none-eabi)	10s
test (1.72.0)	20s
build (stable, wasm32-unknown-unknown)	15s
test (stable)	42s
minimal-versions / minimal-versions	29s
	2m 37s

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