ci: codecov v6

Author: g105b

.github/workflows/ci.yml

@@ -94,7 +94,7 @@ jobs:
         run: cat "_coverage/coverage.txt"
 
       - name: Upload to Codecov
-        uses: codecov/codecov-action@v5
+        uses: codecov/codecov-action@v6
         with:
           token: ${{ secrets.CODECOV_TOKEN }}
           slug: ${{ github.repository }}