Merge pull request #124 from phonopy/dependabot/github_actions/codecov/codecov-action-6

Bump codecov/codecov-action from 5 to 6

Author: lan496

.github/workflows/testing.yml

@@ -46,7 +46,7 @@ jobs:
 
     - name: Upload coverage to Codecov
       if: matrix.python-version == '3.13'
-      uses: codecov/codecov-action@v5
+      uses: codecov/codecov-action@v6
       with:
         file: ./coverage.xml
         flags: unittests