fix: mesop/pip_package/requirements.txt to reduce vulnerabilities (#1078)

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-WERKZEUG-8309091
- https://snyk.io/vuln/SNYK-PYTHON-WERKZEUG-8309092

Co-authored-by: snyk-bot <[email protected]>

Author: wwwillchen

mesop/pip_package/requirements.txt

@@ -6,3 +6,4 @@ protobuf
 pydantic
 python-dotenv
 watchdog # used by mesop CLI for hot reloading
+werkzeug>=3.0.6 # not directly required, pinned by Snyk to avoid a vulnerability