Fix CI: upgrade CodeCov action to v5

Author: mathieu17g

.github/workflows/CI.yml

@@ -67,7 +67,7 @@ jobs:
       - uses: julia-actions/julia-processcoverage@v1
 
       # Upload coverage to Codecov (update to v4)
-      - uses: codecov/codecov-action@v4
+      - uses: codecov/codecov-action@v5
         with:
           files: lcov.info
           token: ${{ secrets.CODECOV_TOKEN }}