Upgrade ES version to build the plugin. (#144)

Author: mashhurs

gradle.properties

@@ -1,2 +1,2 @@
 LOGSTASH_PATH=../../ls
-ELASTICSEARCH_TREEISH=8.12
+ELASTICSEARCH_TREEISH=8.13

logstash-filter-elastic_integration.gemspec

@@ -9,8 +9,8 @@ Gem::Specification.new do |s|
   s.description = "This gem is a Logstash plugin required to be installed on top of the Logstash core pipeline using $LS_HOME/bin/logstash-plugin install gemname. This gem is not a stand-alone program"
   s.authors = ["Elastic"]
   s.email = '[email protected]'
-  s.homepage = "http://www.elastic.co/guide/en/logstash/current/index.html"
-  s.require_paths = ["lib", "vendor/jar-dependencies"]
+  s.homepage = "https://www.elastic.co/logstash"
+  s.require_paths = %w[lib vendor/jar-dependencies]
 
   # Files to be included in package
   s.files = Dir[*%w{