Bump codecov/codecov-action from 5 to 6 in the actions group (#131)

Bumps the actions group with 1 update: [codecov/codecov-action](https://github.com/codecov/codecov-action).

Author: dependabot[bot]

.github/workflows/coverage.yml

@@ -31,4 +31,4 @@ jobs:
           python -m pytest --cov=yaml2ics --doctest-modules --durations=20
 
       - name: Upload to codecov
-        uses: codecov/codecov-action@v5
+        uses: codecov/codecov-action@v6