Github user tamaashu commented on the issue:
https://github.com/apache/zookeeper/pull/663
Thanks @lvfangmin and @eolivelli to pointing this out. 2.6.0 was a typo in
the master branch (should have been 3.6.0, will fix it in master tomorrow) and
got backported here accidentally.
3.5.4 is just a fix for it.
The version number is only added to the pom.xml to be fine, it doesn't
change anything during the document generation, but still I would keep the
proper version number.---
