Make zeroize's version more compatible

[lei2022]

As seen in "aes-gcm-siv/Cargo.toml", zeroize is a dependency and has a hard requirement of ">=1, <1.4": { version = ">=1, <1.4", default-features = false }. It is not compatible with versions >= 1.5. Please consider making it "zeroize = { version = "1", default-features = false }" so it is more compatible.

The latest zeroize version as of this Issue is https://crates.io/crates/zeroize/1.5.4

[tarcieri]

Dup of #377

See also: RustCrypto/utils#723