Pin codecov/codecov-action to v3.1.5

Author: hugovk

.github/workflows/test.yml

@@ -36,7 +36,7 @@ jobs:
           tox -e py
 
       - name: Upload coverage
-        uses: codecov/codecov-action@v4
+        uses: codecov/codecov-action@v3.1.5
         with:
           flags: ${{ matrix.os }}
           name: ${{ matrix.os }} Python ${{ matrix.python-version }}