Bump authlib from 1.6.0 to 1.6.4 in /ai/gen-ai-agents/custom-rag-agent

Bumps [authlib](https://github.com/authlib/authlib) from 1.6.0 to 1.6.4.
- [Release notes](https://github.com/authlib/authlib/releases)
- [Changelog](https://github.com/authlib/authlib/blob/main/docs/changelog.rst)
- [Commits](authlib/authlib@v1.6.0...v1.6.4)

---
updated-dependencies:
- dependency-name: authlib
  dependency-version: 1.6.4
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

ai/gen-ai-agents/custom-rag-agent/requirements.txt

@@ -13,7 +13,7 @@ astroid==3.3.8
 asttokens==3.0.0
 async-lru==2.0.4
 attrs==25.1.0
-Authlib==1.6.0
+Authlib==1.6.4
 babel==2.17.0
 backoff==2.2.1
 beautifulsoup4==4.13.3