chore(deps): update dependency certifi to v2020 (#4)

Co-authored-by: Renovate Bot <bot@renovateapp.com>

Author: renovate[bot]

requirements.txt

@@ -1,4 +1,4 @@
-certifi==2019.11.28
+certifi==2020.4.5.1
 chardet==3.0.4
 idna==2.9
 requests==2.23.0