02_07_05 is current for auto update classes ALPHA, BETA and MINOR. MAJOR is still 02_06_06.
If you want to revert to 02_06_06, you can just change your auto update class to MAJOR.
If you want to revert to another release, see this How to Update Manually post.
Be advised that 02_07 contained functionality that is not supported in 02_06. Specifically integrators and related Script functions will not work.