Bump flask from 1.0 to 2.3.2 in /demo-flask

Bumps [flask](https://github.com/pallets/flask) from 1.0 to 2.3.2.
- [Release notes](https://github.com/pallets/flask/releases)
- [Changelog](https://github.com/pallets/flask/blob/main/CHANGES.rst)
- [Commits](pallets/flask@1.0...2.3.2)

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

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

demo-flask/requirements.txt

@@ -1 +1 @@
-flask==1.0
+flask==2.3.2