Bump certifi from 2020.4.5.2 to 2020.6.20
Bump certifi from 2020.4.5.2 to 2020.6.20

Bumps [certifi](https://github.com/certifi/python-certifi) from 2020.4.5.2 to 2020.6.20.
- [Release notes](https://github.com/certifi/python-certifi/releases)
- [Commits](https://github.com/certifi/python-certifi/compare/2020.04.05.2...2020.06.20)

Signed-off-by: dependabot-preview[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
hypothesis/bouncer,hypothesis/bouncer,hypothesis/bouncer