fix: ensure redis secrets flow from vault

deployment/ansible/secrets/production.vault.yml.example

@@ -8,9 +8,11 @@ vault_db_password: "change-me-secure-db-password"
 vault_db_root_password: "change-me-secure-root-password"
 
 # Application Stack Credentials
+# Required: used for the application stack (.env) and injected into PHP containers
 vault_redis_password: "change-me-secure-redis-password"
 
 # Application Secrets
+# Required: base64 encoded 32 byte key used for APP_KEY
 vault_app_key: "change-me-base64-encoded-32-byte-key"
 vault_jwt_secret: "change-me-jwt-signing-secret"