Make kubectl installation optional

[macmiranda]

In new ubuntu images kubectl is already installed and supersedes the one installed by this action

[macmiranda]

Actually, what I just said isn't true but there is something weird with tag v1.5.0 The release notes and the commit history both show that in this release kubectl version should be 1.25.5 but I'm getting the old 1.23.12 If I use the kubectl_version input override, it works

[macmiranda]

In this line, the default value overrides the default in the shell script https://github.com/helm/kind-action/blob/ab62653af4d7967d7ce31b5eb99214de033d6815/action.yml#L33

[macmiranda]

@cpanato