upgrade gevent due to CI error

Author: mrlevitas

requirements-transitive.txt

@@ -8,7 +8,7 @@ chardet==4.0.0
 click==7.1.2
 coverage==5.3.1
 docutils==0.16
-gevent==20.12.0
+gevent==21.12.0
 greenlet==1.1.1
 idna==2.10
 imagesize==1.2.0