Bump flask from 3.1.0 to 3.1.3 in /sample-apps/quart-postgres-uvicorn

Bumps [flask](https://github.com/pallets/flask) from 3.1.0 to 3.1.3.
- [Release notes](https://github.com/pallets/flask/releases)
- [Changelog](https://github.com/pallets/flask/blob/main/CHANGES.rst)
- [Commits](pallets/flask@3.1.0...3.1.3)

---
updated-dependencies:
- dependency-name: flask
  dependency-version: 3.1.3
  dependency-type: indirect
...

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Author: dependabot[bot]