On remove-log-addressing branch: Further cleanup now unused code.

* subversion/libsvn_fs_fs/transaction.c
  (auto_truncate_proto_rev): Remove empty function.
  (get_writable_proto_rev): Remove call to auto_truncate_proto_rev().


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/remove-log-addressing@1604114 13f79535-47bb-0310-9956-ffa450edef68