fix: restore fernet key length comment in dereference module

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: adwk67

rust/operator-binary/src/controller/dereference.rs

@@ -89,6 +89,10 @@ pub async fn dereference(
     .await
     .context(InvalidInternalSecretSnafu)?;
 
+    // https://airflow.apache.org/docs/apache-airflow/stable/security/secrets/fernet.html#security-fernet
+    // does not document how long the fernet key should be, but recommends using
+    // python -c "from cryptography.fernet import Fernet; print(Fernet.generate_key().decode())"
+    // which returns `jUm21LuA76YZmrIa9u4eXRg0h0P24MDC9IDOmDvJbfw=`, which has 44 characters, which makes 32 bytes.
     random_secret_creation::create_random_secret_if_not_exists(
         &airflow.shared_fernet_key_secret_name(),
         FERNET_KEY_SECRET_KEY,