SOLR-6323: Updated CHANGES.txt

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_5x@1640262 13f79535-47bb-0310-9956-ffa450edef68
SOLR-6684: Updated CHANGES.txt

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_5x@1640265 13f79535-47bb-0310-9956-ffa450edef68