Update coverage workflow for Tox 4

Author: AA-Turner

.github/workflows/coverage.yml

@@ -27,9 +27,10 @@ jobs:
       run: python -m pip install -U pip tox pytest-cov
 
     - name: Run Tox
-      run: tox --sitepackages -e py -- -vv
+      run: tox -e py -- -vv
       env:
         PYTEST_ADDOPTS: "--cov ./ --cov-append --cov-config pyproject.toml"
+        VIRTUALENV_SYSTEM_SITE_PACKAGES: "1"
 
     - name: codecov
       uses: codecov/codecov-action@v3