There's a closed pull request on the void-packages repository

Flask: update to 3.0, clean up stale dependants
https://github.com/void-linux/void-packages/pull/46736

Description:
Flask and Werkzeug 3 drop some deprecated interfaces and break some old packages, but a lot of these are effectively dead anyway.

## Testing the changes
- I tested the changes in this PR: **in progress**

The results of `xbps-src` check on the dependants of `python3-Flask` and `python3-Werkzeug` are noted below.

### Flask dependants
- [ ] etesync-dav (no tests; version restrictions on Flask-WTF have been violated since 2022-09-07)
- [ ] mkchromecast (no tests, maybe abandonware)
- [ ] python3-Flask-HTTPAuth (no tests)
- [ ] python3-Flask-RESTful (tests are broken with Python 3.12)
- [ ] voltron (test framework uncertain)
- [x] OpenLP (23 pre-existing failures, 17 pre-existing errors)
- [x] fava (4 pre-existing failures)
- [x] grip
- [x] impacket (1396 pre-existing failures)
- [x] mitmproxy (3 pre-existing failures)
- [x] python3-Flask-Babel
- [x] python3-Flask-Cors
- [x] python3-Flask-Login
- [x] python3-Flask-WTF
- [x] python3-httpbin

### Werkzeug Dependants
- [x] python3-openapi-core
- [x] python3-pytest-httpserver
- [x] python3-pytest-localserver
- [x] python3-quart

## Removed Packages
- python3-Flask-User
- python3-Flask-Mail
- python3-Flask-Script
- python3-Flask-OAuthlib
- python3-Flask-Assets
- python3-Flask-SQLAlchemy
- python3-stormssh