Update python version matrix for CI

Author: jhodges10

.circleci/config.yml

@@ -15,7 +15,7 @@ workflows:
             - build
           matrix:
             parameters:
-              python-version: ["2.7.16", "2.7.18", "3.5.10", "3.6.5", "3.7.7", "3.8.3", "latest"]
+              python-version: ["2.7.16", "2.7.18", "3.5.10", "3.6.5", "3.7.7", "3.8.6", "3.9.3", "latest"]
 
       - hold:
           type: approval