Polished POM files to remove redundant entries that were causing warnings in the IDE. Some notable changes are:
- Removed spring-boot.version from sample project as they inherit it from the parent
- Removed versioning for maven-jar-plugin (was 3.0) from multiple project so it relies on the managed version
- Removed java.version from all spring-cloud-function-* modules as they inherit the one from parent.
Addressed PR comments
- removed references to maven-jar-plugin
