Tweak comments, no functional change.

* subversion/include/svn_fs.h
  (svn_fs_lock_many, svn_fs_unlock_many): Tweak docs.

* subversion/include/svn_repos.h
  (svn_repos_fs_lock_many, svn_repos_fs_unlock_many): Tweak docs.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1584368 13f79535-47bb-0310-9956-ffa450edef68