Update requrements.in to specify urllib3>=1.24.3

Author: echarrod

requirements.in

@@ -9,7 +9,7 @@ pyopenssl==18.0.0
 PyYAML==5.2 # PyYAML 5.3 does not support Python 3.4
 pytz==2018.9
 requests>=2.20.0
-urllib3>=1.24.2
+urllib3>=1.24.3
 deprecated==1.2.6
 wheel==0.24.0
 iso8601==0.1.12