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

This reverts commit 4f680cf0e8fe6d2e6f205e2fcb963c6a31fc5da8.
Revert "[maven-release-plugin] prepare release 6.2.1"

This reverts commit 5d52149b1be9661a41d5a51c255b99e0ed1958a8.