Spring Fix Kotlin example for static factory method

https://docs.spring.io/spring-framework/docs/current/reference/html/core.html#beans-factory-class-static-factory-method

kotlin changed to:

class ClientService private constructor() {
    companion object {
        private val clientService = ClientService()
        @JvmStatic
        fun createInstance() = clientService
    }
}

Comment From: sbrannen

Hi @SchroedingersGitHub,

Congratulations on opening your first GitHub issue "ever". 👍

This has been addressed in 48c797e429dc26c8156c92cba409c3be07aa6498.