We should change the Kotlin language version to 1.7, see [here](https://github.com/spring-projects/spring-framework/blob/933965b7b4b608b7fb6214d25e5c71bbe674cecb/build.gradle#L280-L281). Doing this allows us to upgrade to Kotlin 1.9 within the 6.0.x timeline.
