Merged revision(s) 1617218 from lucene/dev/trunk:
SOLR-6360: Remove bogus "Content-Charset" header in HttpSolrServer

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1617219 13f79535-47bb-0310-9956-ffa450edef68