Bump flask from 1.1.2 to 2.3.2 in /examples/AsyncProgressBar

Bumps [flask](https://github.com/pallets/flask) from 1.1.2 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@1.1.2...2.3.2)

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

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

examples/AsyncProgressBar/requirements.txt

@@ -2,7 +2,7 @@ aioflask
 aioredis==1.3.1
 async-timeout==3.0.1
 click==7.1.2
-Flask==1.1.2
+Flask==2.3.2
 greenlet==0.4.16
 greenletio
 h11==0.9.0