Cannot drag and drop tasks to sort in pipeline editor

Describe the bug I cannot drag and drop tasks to sort in pipeline editor.

Versions used(KubeSphere/Kubernetes) KubeSphere: v3.1.0

To Reproduce Steps to reproduce the behavior:

1. Go to 'Pipeline Editor'
2. Create some tasks
3. Try to drag and drop tasks to sort
4. No effect

Expected behavior Make tasks sortable.

/kind bug /area devops /priority low