Bump certifi from 2019.9.11 to 2019.11.28 in /requirements (#5909)

Bumps [certifi](https://certifi.io/) from 2019.9.11 to 2019.11.28.

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

requirements/common.txt

@@ -228,9 +228,9 @@ urllib3==1.25.3 \
     --hash=sha256:b246607a25ac80bedac05c6f282e3cdaf3afb65420fd024ac94435cabe6e18d1 \
     --hash=sha256:dbe59173209418ae49d485b87d1681aefa36252ee85884c31346debd19463232
 
-certifi==2019.9.11 \
-    --hash=sha256:fd7c7c74727ddcf00e9acd26bba8da604ffec95bf1c2144e67aff7a8b50e6cef \
-    --hash=sha256:e4f3620cfea4f83eedc95b24abd9cd56f3c4b146dd0177e83a21b4eb49e21e50
+certifi==2019.11.28 \
+    --hash=sha256:017c25db2a153ce562900032d5bc68e9f191e44e9a0f762f373977de9df1fbb3 \
+    --hash=sha256:25b64c7da4cd7479594d035c08c2d809eb4aab3a26e5a990ea98cc450c320f1f
 
 # required by requests
 chardet==3.0.4 \