[Gem] Updates meta header test

Author: picandocodigo

elasticsearch/spec/integration/client_integration_spec.rb

@@ -51,7 +51,7 @@
   context 'Reports the right meta header' do
     it 'Reports es service name and gem version' do
       headers = client.transport.transport.connections.first.connection.headers
-      expect(headers['x-elastic-client-meta']).to match /^es=#{Elasticsearch::VERSION}/
+      expect(headers['x-elastic-client-meta']).to match Elastic.client_meta_version
     end
   end
 end