CI: Remove undefined variable in qmake config

Author: jamesobutler

.github/workflows/build_latest.yml

@@ -122,7 +122,6 @@ jobs:
         python --version
         qmake CONFIG+=release CONFIG-=debug_and_release CONFIG-=debug_and_release_target ^
            CONFIG+=exclude_generator ^
-           "PYTHONQTALL_CONFIG=${{ matrix.pythonqtall-config }}" ^
            "PYTHON_PATH=%pythonLocation%" ^
            "PYTHON_VERSION=${{ steps.setenv.outputs.PYTHON_VERSION_SHORT }}" ^
            PythonQt.pro