v0.10.0 crane dashboard "Add Cluster view" the required field validation prompt is incorrect

[JaneConan]

Describe the bug "Add Cluster view" the required field validation prompt is incorrect.

if we change Discount value < 0

Reproduce steps

1. open the "Add Cluster view"
2. click "Confirm" button
3. show the prompted.

Expected behavior

Screenshots

Environment (please complete the following information):

• K8S Version: [e.g. 1.19]
• Crane Version: [e.g. 0.1.0]
• Browser [e.g. chrome, safari]