remove Python 3.6 from actions

Author: jGaboardi

.github/workflows/unittests.yml

@@ -16,10 +16,7 @@
      strategy:
        matrix:
          os: ['macos-latest', 'ubuntu-latest', 'windows-latest']
-         environment-file: [ci/36.yaml, ci/37.yaml, ci/38.yaml, ci/39.yaml]
-         exclude:
-           - environment-file: ci/36.yaml
-             os: windows-latest
+         environment-file: [ci/37.yaml, ci/38.yaml, ci/39.yaml]
 
      steps:
        - name: checkout repo