SpringBoot Kotlin plugin's version shouldn't be read if the kotlin.version extra property has been set

We read it at the moment and then don't use it if kotlin.version has been set. This is slightly wasteful and prevents setting kotlin.version from being a workaround for problems like https://github.com/spring-projects/spring-boot/issues/26864.

Comment From: materemias

@wilkinsona is this expected in 2.5.2 too?

Comment From: snicoll

@materemias all fixes are merged forward obviously, see the reference to #26947 above your comment.

Comment From: materemias

got it, thanks!