Bump certifi from 2020.12.05 to 2021.5.30

Bumps [certifi](https://github.com/certifi/python-certifi) from 2020.12.05 to 2021.5.30.
- [Release notes](https://github.com/certifi/python-certifi/releases)
- [Commits](https://github.com/certifi/python-certifi/compare/2020.12.05...2021.05.30)

---
updated-dependencies:
- dependency-name: certifi
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

requirements.txt

@@ -1,4 +1,4 @@
-certifi==2020.12.05
+certifi==2021.5.30
 babel==2.9.1
 flask-babel==2.0.0
 flask==1.1.2