Update flask requirement from ~=3.0 to ~=3.1

Updates the requirements on [flask](https://github.com/pallets/flask) to permit the latest version.
- [Release notes](https://github.com/pallets/flask/releases)
- [Changelog](https://github.com/pallets/flask/blob/main/CHANGES.rst)
- [Commits](pallets/flask@3.0.0...3.1.0)

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

Signed-off-by: dependabot[bot] <[email protected]>

requirements.txt

@@ -2,7 +2,7 @@
 # SPDX-License-Identifier: MIT
 
 bootstrap-flask~=2.4
-flask~=3.0
+flask~=3.1
 flask-limiter[redis]~=3.8
 flask-wtf~=1.2
 gunicorn[eventlet]~=23.0