SOLR-5540: Move CHANGES entry to 4.6 branch

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1557849 13f79535-47bb-0310-9956-ffa450edef68
clean up CHANGES

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1557853 13f79535-47bb-0310-9956-ffa450edef68