chore(images/fluentd): remove elasticsearch upstream gem

Signed-off-by: Bence Csati <bence.csati@axoflow.com>

Author: csatib02

images/fluentd/outputs/Gemfile

@@ -5,7 +5,6 @@ gem 'fluent-plugin-kafka', '0.19.5'
 gem 'fluent-plugin-grafana-loki', '1.2.20'
 gem 'fluent-plugin-kinesis', '3.6.1'
 gem 'fluent-plugin-splunk-hec', '1.3.3'
-gem 'fluent-plugin-elasticsearch', '6.0.0'
 gem 'fluent-plugin-newrelic', '1.2.3'
 gem 'fluent-plugin-cloudwatch-logs', '0.15.0'
 gem 'fluent-plugin-opensearch', '1.1.5'