ci: restrict Codecov upload to Ubuntu environment only

Author: bartventer

.github/workflows/default.yml

@@ -31,7 +31,7 @@ jobs:
         run: make test
 
       - name: Upload coverage reports to Codecov
-        if: ${{ github.event_name == 'push' && github.ref == 'refs/heads/master' }}
+        if: ${{ github.event_name == 'push' && github.ref == 'refs/heads/master' && matrix.os == 'ubuntu-latest' }}
         uses: codecov/codecov-action@0565863a31f2c772f9f0395002a31e3f06189574 # v5.4.0
         with:
           token: ${{ secrets.CODECOV_TOKEN }}