To convert your OpenBeta to release, do
bin\DCS_updater.exe update @release
The menu entries will still say OpenBeta though.
So take this as a warning that you may end up with a version which says OpenBeta
in the folder name and the menu shortcuts, while being, in fact, on the 'release' channel of the updater.
Actually, better NOT do this.
A MUCH better solution:
Just install the release, it will pick up the files from the openbeta, and delete openbeta after that.