Follow-up to r1589518.

* subversion/libsvn_fs_fs/fs.c
  (fs_serialized_init): Re-instantiate the comment removed in r1589262.

Found by: kotkov

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1617586 13f79535-47bb-0310-9956-ffa450edef68