Update KindToResource impl to match API server

[liggitt]

k8s PR 16221 upstream changed KindToResource handling of kinds ending in "s", so we'll need to carry an exception for "securitycontextconstraints" and match this impl:

// KindToResource converts Kind to a resource name.
func KindToResource(kind string, mixedCase bool) (plural, singular string) {
    if len(kind) == 0 {
        return
    }
    if mixedCase {
        // Legacy support for mixed case names
        singular = strings.ToLower(kind[:1]) + kind[1:]
    } else {
        singular = strings.ToLower(kind)
    }
    if strings.HasSuffix(singular, "endpoints") || strings.HasSuffix(singular, "securitycontextconstraints") {
        plural = singular
    } else {
        switch string(singular[len(singular)-1]) {
        case "s":
            plural = singular + "es"
        case "y":
            plural = strings.TrimSuffix(singular, "y") + "ies"
        default:
            plural = singular + "s"
        }
    }
    return
}