Docs: Missing secret_key in XChaCha20 docs
// SOFTWARE.
//! # Parameters:
-//! - `key`: The secret key
+//! - `secret_key`: The secret key
//! - `nonce`: The nonce value
//! - `initial_counter`: The initial counter value. In most cases this is `0`
//! - `ciphertext`: The encrypted data
//!
//! # Exceptions:
//! An exception will be thrown if:
-//! - The length of the `key` is not `32` bytes
+//! - The length of the `secret_key` is not `32` bytes
//! - The length of the `nonce` is not `24` bytes
//! - The length of `dst_out` is less than `plaintext` or `ciphertext`
//! - `plaintext` or `ciphertext` are empty
