LUCENE-5944: Remove the version constant. The problem was the broken logic in TestBackwardsCompatibility to detect "Lucene trunk" which has an additional unreleased index before Version.LATEST: I will open issue, maybe Ryan has better idea.

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_5x@1626188 13f79535-47bb-0310-9956-ffa450edef68