Build: revert the need to use a git source (#302)

Author: kares

.ci/setup.sh

@@ -9,6 +9,3 @@ if Dir.exist?(logstash_path) && use_logstash_source
   gem 'logstash-core', :path => "#{logstash_path}/logstash-core"
   gem 'logstash-core-plugin-api', :path => "#{logstash_path}/logstash-core-plugin-api"
 end
-
-# TODO till filter grok with ECS support is released :
-gem 'logstash-filter-grok', git: 'https://github.com/kares/logstash-filter-grok.git', ref: 'ecs-1-support'