As of As of spring-projects/spring-framework#35733, Spring Framework has
a dedicated method for configuring a Kotlin Serialization converter
specifically.
This commit uses this method instead of configuring the Kotlin
Serialization JSON support as a custom converter. This also removes the
`@Order` on the Kotlin converter bean itself, as there is no need to
order it in the list of custom converters anymore.
Closes gh-47917