Update codecov/codecov-action action to v5

Author: renovate[bot]

.github/workflows/unittests.yml

@@ -55,4 +55,4 @@ jobs:
         if: "${{ matrix.python-version == '3.11' }}"
         env:
           CODECOV_TOKEN: ${{secrets.CODECOV_TOKEN}}
-        uses: codecov/codecov-action@v2
+        uses: codecov/codecov-action@v5