🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

Author: gcf-owl-bot[bot]

.kokoro/presubmit/prerelease-deps.cfg

@@ -5,9 +5,3 @@ env_vars: {
     key: "NOX_SESSION"
     value: "prerelease_deps"
 }
-
-# Credentials needed to test universe domain.
-env_vars: {
-  key: "SECRET_MANAGER_KEYS"
-  value: "client-library-test-universe-domain-credential"
-}