Revert "[RELEASE 6.1.0-rc-19] Prepare next development version 6.1.0-SNAPSHOT"

This reverts commit cd857587dde2e4988108cecb678b4351b8cdd0cd.
Revert "[RELEASE 6.1.0-rc-19] Create release 6.1.0-rc-19"

This reverts commit 98189db8673dbea2a613bb53e3324da4e99e698c.