Elasticsearch 5: Remove core POM change

This commit removes an unrelated POM change for the original
(Elasticsearch 2) binding.

pom.xml

@@ -91,7 +91,6 @@ LICENSE file.
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <thrift.version>0.8.0</thrift.version>
     <hypertable.version>0.9.5.6</hypertable.version>
-    <elasticsearch-version>2.4.4</elasticsearch-version>                                                                                                                                      
     <elasticsearch5-version>5.5.1</elasticsearch5-version>
     <couchbase.version>1.4.10</couchbase.version>
     <couchbase2.version>2.3.1</couchbase2.version>