[Feature] Update doc for GCS FT after API changes

### Search before asking

- [X] I had searched in the [issues](https://github.com/ray-project/kuberay/issues) and found no similar feature requirement.


### Description

as title

### Use case

as title

### Related issues

_No response_

### Are you willing to submit a PR?

- [ ] Yes I am willing to submit a PR!