Use supported Kubernetes Version instead of latest

[smuu]

https://github.com/celestiaorg/knuu/blob/cb478fc1fb7786f527776aec4680cb8a30bf1abb/pkg/knuu/knuu.go#L92

Currently, the latest image is used, which could cause issues with compatibility. Instead, use an image with the supported Kubernetes version.

Ref.: https://github.com/celestiaorg/knuu/issues/29

[tty47]

create a function to get the k8s version from API and return it, then, use the value to generate the image name