fix: Add MacOS back into the test matrix

Author: mpenning

.github/workflows/tests.yml

@@ -49,7 +49,6 @@ jobs:
       - name: 'Display Python version'
         run: 'python -c ''import sys; print(sys.version)'''
       - name: 'Install dependencies on Ubuntu Linux / Windows / MacOS'
-        if: '${{ matrix.os != ''macos-latest'' }}'
         run: |
           true  ###############################################################
           true  # install pip, and uv