Draft: Revert to gemnasium-maven-plugin 0.5.1

What does this MR do?

This is to ensure that, prior to gemnasium-maven-plugin 0.6.0, integration tests if we remove the mvn install command.

What are the relevant issue numbers?

See gitlab-org/gitlab#432914 (closed)

Does this MR meet the acceptance criteria?

No intended to be merged.