On the log-addressing branch:  Fix / update L2P index documentation.

* subversion/libsvn_fs_fs/structure-indexes
  (Log-to-phys index.Index data model): remove duplicate word
  (Log-to-phys index.Index file format): fix off-by-one mismatch between
                                         code and documentation


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/log-addressing@1537174 13f79535-47bb-0310-9956-ffa450edef68