Remove a couple of unused fields from the FSFS stats internal data model.

* subversion/libsvn_fs_fs/stats.c
  (rep_stats_t): Remove write-only members.
  (parse_representation): No longer write those fields.

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1632852 13f79535-47bb-0310-9956-ffa450edef68