HBASE-27453 Update downloads.xml for release 2.4.15
HBASE-27453 Update downloads.xml for release 2.4.15

ndimiduk/hbase,Apache9/hbase,Apache9/hbase,mahak/hbase,mahak/hbase,Apache9/hbase,mahak/hbase,mahak/hbase,ndimiduk/hbase,mahak/hbase,Apache9/hbase,ndimiduk/hbase,Apache9/hbase,ndimiduk/hbase,ndimiduk/hbase,Apache9/hbase,mahak/hbase,mahak/hbase,mahak/hbase,ndimiduk/hbase,ndimiduk/hbase,ndimiduk/hbase,mahak/hbase,Apache9/hbase,Apache9/hbase,Apache9/hbase,Apache9/hbase,ndimiduk/hbase,mahak/hbase,ndimiduk/hbase