build: remove support for python 2.7 in ci

Author: lucagiove

.github/workflows/pythonapp.yml

@@ -11,7 +11,7 @@ jobs:
     strategy:
       matrix:
         os: [ ubuntu-latest, macos-latest, windows-latest ]
-        python-version: [ 2.7, 3.7, 3.8, 3.x ]
+        python-version: [ 3.7, 3.8, 3.x ]
     steps:
       - uses: actions/checkout@v2
       - name: Set up Python