Revert "[maven-release-plugin] prepare release 2.1.2"

This reverts commit 8c3ec046cf5c7273a439dd6a395fb9af97c2caf0.
Revert "[maven-release-plugin] prepare for next development iteration"

This reverts commit e70dfbc45f7ccf4a42c4ed9b48b6a3b822abc898.