chore(deps): bump python-telegram-bot from 21.5 to 21.6

Bumps [python-telegram-bot](https://github.com/python-telegram-bot/python-telegram-bot) from 21.5 to 21.6.
- [Release notes](https://github.com/python-telegram-bot/python-telegram-bot/releases)
- [Changelog](https://github.com/python-telegram-bot/python-telegram-bot/blob/master/CHANGES.rst)
- [Commits](https://github.com/python-telegram-bot/python-telegram-bot/compare/v21.5...v21.6)

---
updated-dependencies:
- dependency-name: python-telegram-bot
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

requirements.txt

@@ -9,7 +9,7 @@ cryptography==42.0.8; platform_machine == 'armv7l'
 cryptography==43.0.1; platform_machine != 'armv7l'
 aiohttp==3.10.5
 SQLAlchemy==2.0.34
-python-telegram-bot==21.5
+python-telegram-bot==21.6
 # can't be hard-pinned due to telegram-bot pinning httpx with ~
 httpx>=0.24.1
 humanize==4.10.0