Revert "[maven-release-plugin] prepare for next development iteration"

This reverts commit b26b17b5975e164466c5650d5e2365dd4efa314e.
Revert "[maven-release-plugin] prepare release 6.2.0-ga1"

This reverts commit f6f3a05bfbdb1a99eca96c09ec65eeb6136e57a7.