On fsfs-improvements branch: Fix typo in comment.

* subversion/libsvn_fs_fs/fs.h (struct pair_cache_key_t): Typo.


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/fsfs-improvements@1510901 13f79535-47bb-0310-9956-ffa450edef68