CI: fix codecov setup

Author: fingolfin

.github/workflows/CI.yml

@@ -39,7 +39,7 @@ jobs:
       - uses: gap-actions/build-pkg@v1
       - uses: gap-actions/run-pkg-tests@v2
       - uses: gap-actions/process-coverage@v2
-      - uses: codecov/codecov-action@v4
+      - uses: codecov/codecov-action@v5
         with:
           token: ${{ secrets.CODECOV_TOKEN }}