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

[baloo]

Depends on:

• https://github.com/RustCrypto/block-ciphers/pull/413

[tarcieri]

Looks like some build failures

[baloo]

@tarcieri could I get a merge on this one? That way I remove the reference to my fork on https://github.com/RustCrypto/formats/pull/1391