Update argon2 requirement from 0.3 to 0.4 (#26)

Updates the requirements on [argon2](https://github.com/RustCrypto/password-hashes) to permit the latest version.
- [Release notes](https://github.com/RustCrypto/password-hashes/releases)
- [Commits](https://github.com/RustCrypto/password-hashes/compare/scrypt-v0.3.0...scrypt-v0.4.1)

---
updated-dependencies:
- dependency-name: argon2
  dependency-type: direct:production
...

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Cargo.toml

@@ -37,7 +37,7 @@ panic = 'abort'
 [dependencies]
 aes-gcm = "0.10"
 anyhow = "1.0"
-argon2 = "0.3"
+argon2 = "0.4"
 base64 = "0.13"
 bincode = "1.3"
 blake3 = "1.3"