Added missing manticore dependency at 'elasticsearch_spec.rb' tests

Author: alexcams

spec/inputs/paginated_search_spec.rb

@@ -1,5 +1,6 @@
 require "logstash/devutils/rspec/spec_helper"
 require "logstash/inputs/elasticsearch/paginated_search"
+require "manticore"
 
 describe "Paginated search" do
   let(:es_client) { double("Elasticsearch::Client") }