cibuildwheel has now python 3.9 support

Author: maxbachmann

.github/workflows/pythonbuild.yml

@@ -67,7 +67,7 @@ jobs:
 
       - name: Install cibuildwheel
         run: |
-          python -m pip install git+https://github.com/joerick/cibuildwheel.git@python3.9
+          python -m pip install cibuildwheel==1.6.0
 
       - name: Build wheels
         run: |