build(deps): bump flask in /samples/server/petstore/python-flask

Bumps [flask](https://github.com/pallets/flask) from 2.1.1 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@2.1.1...3.1.3)

---
updated-dependencies:
- dependency-name: flask
  dependency-version: 3.1.3
  dependency-type: direct:production
...

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

Author: dependabot[bot]

samples/server/petstore/python-flask/requirements.txt

@@ -10,4 +10,4 @@ werkzeug == 0.16.1; python_version=="3.5" or python_version=="3.4"
 swagger-ui-bundle >= 0.0.2
 python_dateutil >= 2.6.0
 setuptools >= 21.0.0
-Flask == 2.1.1
+Flask == 3.1.3