[BUG] PyTorchJob create pod failure due to pod webhook

[zmberg]

What happened:

1. create PyTorchJob

apiVersion: kubeflow.org/v1
kind: PyTorchJob
metadata:
  name: pytorch-tcp-dist-mnist
spec:
  pytorchReplicaSpecs:
    Master:
      replicas: 1
      restartPolicy: OnFailure
      template:
        metadata:
          labels:
            app: tfjob
        spec:
          terminationGracePeriodSeconds: 0
          containers:
            - command: [ "/bin/sleep", "infinity" ]
              image: busybox:latest
              name: pytorch

2. describe PyTorchJob

  Warning  FailedCreatePod  108s (x17 over 7m15s)  pytorchjob-controller  Error creating: admission webhook "mpod.kb.io" denied the request: Internal error occurred: the spec replicas field ".spec.pytorchReplicaSpecs.Worker.replicas" does not exist

What you expected to happen:

How to reproduce it (as minimally and precisely as possible):

Anything else we need to know?:

Environment:

• Kruise version: v1.6.3
• Kubernetes version (use kubectl version):
• Install details (e.g. helm install args):
• Others: