try to fix codecov (pydata#1717)

see if this fixes codecov

Author: drammock

.github/workflows/tests.yml

@@ -93,7 +93,7 @@ jobs:
       - name: Run tests
         run: pytest -m "not a11y" --color=yes --cov --cov-report=xml
       - name: Upload to Codecov
-        if: matrix.python-version == '3.12' && matrix.os == 'ubuntu-latest'
+        if: matrix.python-version == '3.12' && matrix.os == 'ubuntu-latest' && matrix.sphinx-version == 'dev'
         uses: codecov/codecov-action@v4
         with:
           token: ${{ secrets.CODECOV_TOKEN }}