Bump certifi from 2017.4.17 to 2019.11.28

Bumps [certifi](https://github.com/certifi/python-certifi) from 2017.4.17 to 2019.11.28.
- [Release notes](https://github.com/certifi/python-certifi/releases)
- [Commits](https://github.com/certifi/python-certifi/compare/2017.04.17...2019.11.28)

Signed-off-by: dependabot-preview[bot] <[email protected]>

requirements.txt

@@ -1,7 +1,7 @@
 backports.shutil_get_terminal_size==1.0.0
 backports.ssl-match-hostname==3.5.0.1; python_version < '3'
 cached-property==1.3.0
-certifi==2017.4.17
+certifi==2019.11.28
 chardet==3.0.4
 colorama==0.4.3; sys_platform == 'win32'
 docker==4.1.0