Bump python-telegram-bot from 21.7 to 21.8

Bumps [python-telegram-bot](https://github.com/python-telegram-bot/python-telegram-bot) from 21.7 to 21.8.
- [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](python-telegram-bot/python-telegram-bot@v21.7...v21.8)

---
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

@@ -1,2 +1,2 @@
 noobstuffs==2.0.7
-python-telegram-bot==21.7
+python-telegram-bot==21.8