Update pycountry requirement from <19.9,>=19.8 to >=19.8,<20.8

Updates the requirements on [pycountry](https://github.com/flyingcircusio/pycountry) to permit the latest version.
- [Release notes](https://github.com/flyingcircusio/pycountry/releases)
- [Changelog](https://github.com/flyingcircusio/pycountry/blob/master/HISTORY.txt)
- [Commits](https://github.com/flyingcircusio/pycountry/compare/19.8.18...20.7.3)

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

requirements.txt

 ipython>=7.12,<7.16
 
 # Country data
-pycountry>=19.8,<19.9
+pycountry>=19.8,<20.8