[requires.io] dependency update

Author: requires

requirements.txt

@@ -34,7 +34,7 @@ pylint-flask==0.5
 pylint-plugin-utils==0.4
 pylint==2.2.2
 PyYAML==3.13              # via inlineplz, prospector
-requests==2.20.1
+requests==2.21.0
 requirements-detector==0.6
 restructuredtext-lint==1.2.1
 scandir==1.9.0