ci(deps): revert bump codecov/codecov-action from 3 to 4 (#849)

This reverts commit b8c0c7c.

Author: DomWeldon

.github/workflows/pythonpackage.yml

@@ -31,7 +31,7 @@ jobs:
         shell: bash
       - name: Upload coverage to Codecov
         if: runner.os == 'Linux'
-        uses: codecov/codecov-action@v4
+        uses: codecov/codecov-action@v3
         with:
           token: ${{secrets.CODECOV_TOKEN}}
           file: ./coverage.xml