Remove plugin version management for exec-maven plugin

[breun]

The Spring Boot 2.3. Release Notes contain a section on Removal of some Maven Plugin Management that says:

Spring Boot’s build no longer makes use of Maven’s exec plugin (exec-maven-plugin) or site plugin (maven-site-plugin) and plugin management for them has been removed. If you were relying on Spring Boot’s managed versions, you should add your own plugin management.

Looking at https://search.maven.org/artifact/org.springframework.boot/spring-boot-dependencies/2.3.1.RELEASE/pom I indeed don't see plugin management for maven-site-plugin anymore, but the entry for exec-maven-plugin is still present. The source for that seems to be https://github.com/spring-projects/spring-boot/blob/master/spring-boot-project/spring-boot-dependencies/build.gradle#L307-L313

I don't know if that was intentional or not, but at least the remark about exec-maven-plugin in the release notes doesn't seem to match the contents of the spring-boot-dependencies POM and projects that use exec-maven-plugin can currently still use Spring Boot's managed version.

[wilkinsona]

Thanks for letting us know. This was unintentional. It was removed from spring-boot-starter-parent in #20883 but we missed removing it from spring-boot-dependencies.

[dreis2211]

I can tackle that later today...

[snicoll]

I am not sure removing the version in 2.3.2 is a good idea. Shouldn't we do this in 2.4 and update the release notes section rather?