jbpm-work-items project dependencyManagement should not use project.version property

When jbpm-work-items project uses ${project.version} property in Dependency management section, there are issues when using the project as a parent in another.

Then user has no easy way of using the parent of certain version (e.g. 7.30.0-SNAPSHOT) and have their own versioning (1.0.0-SNAPSHOT) of the actual Work Item Handler. Because what happens is, that project.version in child project overrides version declaration inherited from the parent one, resulting in Maven build looking for incorrect dependencies.

The version management of jbpm-work-items needs to get rid of the ${project.version} property usage.