Investigate how to tune checkstyle on doc samples

[snicoll]

See #45554

It would be nice if basic things such as unused imports and the like were enabled.

[wilkinsona]

I believe they already are as we only have a few suppressions for spring-boot-docs. I think the problem was that this was Kotlin code and Checkstyle only checks Java code.

[snicoll]

🤦