Remove python 3.7 from CI (#54)

it's not available on Ubuntu anymore since it's EOL

Author: AaronAtDuo

.github/workflows/openvpn-ci.yml

@@ -14,7 +14,7 @@ jobs:
 
     strategy:
       matrix:
-        python-version: ["3.7", "3.8", "3.9", "3.10"]
+        python-version: ["3.8", "3.9", "3.10"]
 
     steps:
       - uses: actions/checkout@v2