CI: fix codecov setup

Author: fingolfin

.github/workflows/CI.yml

@@ -45,7 +45,7 @@ jobs:
         with:
           only-needed: true
       - uses: gap-actions/process-coverage@v2
-      - uses: codecov/codecov-action@v4
+      - uses: codecov/codecov-action@v5
         with:
           token: ${{ secrets.CODECOV_TOKEN }}