Bump python-dotenv in /samples/web-app-managed-identity/python/src (#87)

Bumps [python-dotenv](https://github.com/theskumar/python-dotenv) from 1.1.1 to 1.2.2.
- [Release notes](https://github.com/theskumar/python-dotenv/releases)
- [Changelog](https://github.com/theskumar/python-dotenv/blob/main/CHANGELOG.md)
- [Commits](theskumar/python-dotenv@v1.1.1...v1.2.2)

---
updated-dependencies:
- dependency-name: python-dotenv
  dependency-version: 1.2.2
  dependency-type: direct:production
...

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Author: dependabot[bot]

samples/web-app-managed-identity/python/src/requirements.txt

@@ -3,4 +3,4 @@ azure-identity==1.16.1
 azure-storage-blob==12.26.0
 azure-core==1.38.0
 gunicorn==23.0.0
-python-dotenv==1.1.1
+python-dotenv==1.2.2