Update main.yml

Roll back Python because of Bezier module

Author: NPoole

.github/workflows/main.yml

@@ -16,7 +16,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v4
         with:
-          python-version: '3.x'
+          python-version: '3.7.1'
 
       - name: Install dependencies
         run: |