Remove Hardcode version in revapi-plugin

In droolsjbpm/droolsjbpm-knowledge.git/kie-api/pom.xml, it is hardcorded upstream released version (ie 6.4.0.Final) in revapi maven plugin to check api compatiblility.

The hardcode version makes the product tool not able to override them into product version.
Hense, it can't be build because only 6.4.0.Final-redhat-8 is the latest version in product build env.

Please use properties (eg like <version.org.kie.latest.replease>6.4.0.Final</version.org.kie.latest.replease>) instead of hardcode version. And ideally the properties should be placed under droolsjbpm-buildbootstrap.

This issue can be verified in Prod build phase, no QE efforts required.