Update version in setup.cfg, not setup.py

Author: wichert

.github/workflows/main.yaml

@@ -66,7 +66,7 @@ jobs:
       - name: Insert version number
         run: |
           version=$(echo $GITHUB_REF | cut -d/ -f3)
-          sed -ie "/^version/s/=.*/= \"$version\"/" setup.py
+          sed -ie "/^version/s/=.*/= $version/" setup.cfg
 
       - name: Generate changelog
         uses: scottbrenner/generate-changelog-action@master