Drop rebootstrap on cloudooo.

Follow up c902ed4b.

stack/cloudooo.cfg

 [buildout]
 extensions =
-  slapos.rebootstrap
   slapos.zcbworkarounds
   buildout-versions
   mr.developer
@@ -90,11 +89,6 @@ develop +=
 [bootstrap2.6]
 python = python2.6
 
-[rebootstrap]
-# Default first version of rebootstrapped python
-version = 3
-section = python2.7
-
 [versions]
 # Use SlapOS patched zc.buildout
 zc.buildout = 1.6.0-dev-SlapOS-006