Previously, dependency management for JNA was provided by
spring-boot-dependencies so it affected users' applications. It was
original added for Elasticsearch but is no longer needed for that
purpose. We use JNA in spring-boot-buildpack-platform which is used
by our Gradle and Maven plugins and should not affect an application's
use of JNA.

This commit moves management of JNA from spring-boot-dependencies into
spring-boot-parent. This means that users' applications will now be
free to use whatever version of JNA meets their needs while still
controlling the version used for image building via Gradle or Maven.

Closes gh-20156