Drop CIBW_ENABLE=all on Travis windows

It doesn't fit into the time limit

Author: joerick

.travis.yml

@@ -45,7 +45,8 @@ jobs:
         - choco upgrade python3 -y --version 3.12.8 --limit-output --params "/InstallDir:C:\\Python312"
       env:
         - PYTHON=C:\\Python312\\python
-        - CIBW_ENABLE=all
+        # a build using CIBW_ENABLE=all does not fit into Travis' time limit,
+        # so only the defaults are tested
 
     - name: Linux | s390x | Python 3.12
       python: 3.12