fix typo

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1450249 13f79535-47bb-0310-9956-ffa450edef68
this is not a typo! it is TREC

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1450253 13f79535-47bb-0310-9956-ffa450edef68