Bump flask from 2.0.1 to 2.2.5 in /nginx-flask-mysql/backend

Bumps [flask](https://github.com/pallets/flask) from 2.0.1 to 2.2.5.
- [Release notes](https://github.com/pallets/flask/releases)
- [Changelog](https://github.com/pallets/flask/blob/main/CHANGES.rst)
- [Commits](https://github.com/pallets/flask/compare/2.0.1...2.2.5)

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

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

nginx-flask-mysql/backend/requirements.txt

@@ -1,2 +1,2 @@
-Flask==2.0.1
+Flask==2.2.5
 mysql-connector==2.2.9