On the 'move-tracking-2' branch: Update a doc string.

* subversion/include/private/svn_editor3.h
  (svn_editor3_delete): Clarify the effect on children and out-of-date checking.

git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/move-tracking-2@1636924 13f79535-47bb-0310-9956-ffa450edef68