remove support for 3.7 because of difference in AST

Author: xnuinside

.github/workflows/main.yml

@@ -32,7 +32,7 @@ jobs:
     needs: [flake8_py3]
     strategy:
       matrix:
-        python: ['3.7', '3.8', '3.9', '3.10', '3.11']
+        python: ['3.8', '3.9', '3.10', '3.11']
     steps:
     - uses: actions/checkout@v2
     - name: Set up Python