Merge pull request #325 from neutrons/remove-18.04

Removing Ubuntu 18.04 from CI/CD

Author: marshallmcdonnell

.github/workflows/actions.yml

@@ -19,7 +19,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-18.04, ubuntu-20.04]
+        os: [ubuntu-20.04]
         python-version: ["3.6"]
 
     steps: