Update yard rake task for Redmine 2.x (#14796).

Contributed by Mischa The Evil.


git-svn-id: http://svn.redmine.org/redmine@13365 e93f8b46-1217-0410-a6f0-8f06a7374b81
Merged r13365 (#14796).


git-svn-id: http://svn.redmine.org/redmine@13366 e93f8b46-1217-0410-a6f0-8f06a7374b81