Only build cpython builds

Author: rhpvorderman

.github/workflows/ci.yml

@@ -146,10 +146,10 @@ jobs:
         name: Install Python
       - name: Install cibuildwheel
         run: python -m pip install cibuildwheel==1.8.0
-        env:
-          CIBW_BUILD: "cp36-* cp37-* cp38-* cp39-*"
       - name: Build wheels
         run: cibuildwheel --output-dir dist
+        env:
+          CIBW_BUILD: "cp3{6,7,8,9}-*"
       - name: Build sdist
         if: "runner.os == 'Linux'"
         run: python setup.py sdist