Update v1beta1 inference examples

[yuzisun]

/kind feature

Describe the solution you'd like
Update api group and kfserving name references in v1beta1 samples.
https://github.com/kubeflow/kfserving/tree/master/docs/samples/v1beta1

Anything else you would like to add:
[Miscellaneous information that will assist in solving the issue.]

[kserve-oss-bot]

@yuzisun: The label(s) kind/feature cannot be applied, because the repository doesn't have them.

In response to this:

/kind feature

Describe the solution you'd like
Update api group and kfserving name references in v1beta1 samples.
https://github.com/kubeflow/kfserving/tree/master/docs/samples/v1beta1

Anything else you would like to add:
[Miscellaneous information that will assist in solving the issue.]

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.