regression writing to DLQ in 11.0.0

[kares]

Logstash information:

Please include the following information:

1. Logstash version - not relevant 11.0.0 wasn't part of any LS version at this point
2. Logstash installation source - manual plugin install
3. How is Logstash being run (e.g. as a service/service manager: systemd, upstart, etc. Via command line, docker/kubernetes)
4. How was the Logstash Plugin installed - manually

Provide logs (if relevant):

[ERROR] 2021-04-19 20:34:04.190 [[test]>worker0] elasticsearch - Encountered an unexpected error submitting a bulk request, will retry {:message=>"class org.jruby.RubyHash cannot be cast to class org.logstash.ext.JrubyEventExtLibrary$RubyEvent (org.jruby.RubyHash and org.logstash.ext.JrubyEventExtLibrary$RubyEvent are in unnamed module of loader 'app')", :exception=>Java::JavaLang::ClassCastException, :backtrace=>["org.logstash.common.AbstractDeadLetterQueueWriterExt$PluginDeadLetterQueueWriterExt.doWrite(AbstractDeadLetterQueueWriterExt.java:199)", "org.logstash.common.AbstractDeadLetterQueueWriterExt.write(AbstractDeadLetterQueueWriterExt.java:67)", "opt.logstash.build.logstash_minus_7_dot_12_dot_1_minus_SNAPSHOT.vendor.bundle.jruby.$2_dot_5_dot_0.gems.logstash_minus_output_minus_elasticsearch_minus_11_dot_0_dot_0_minus_java.lib.logstash.plugin_mixins.elasticsearch.common.RUBY$method$handle_dlq_status$0(/opt/logstash/build/logstash-7.12.1-SNAPSHOT/vendor/bundle/jruby/2.5.0/gems/logstash-output-elasticsearch-11.0.0-java/lib/logstash/plugin_mixins/elasticsearch/common.rb:204)", "opt.logstash.build.logstash_minus_7_dot_12_dot_1_minus_SNAPSHOT.vendor.bundle.jruby.$2_dot_5_dot_0.gems.logstash_minus_output_minus_elasticsearch_minus_11_dot_0_dot_0_minus_java.lib.logstash.plugin_mixins.elasticsearch.common.RUBY$block$submit$1(/opt/logstash/build/logstash-7.12.1-SNAPSHOT/vendor/bundle/jruby/2.5.0/gems/logstash-output-elasticsearch-11.0.0-java/lib/logstash/plugin_mixins/elasticsearch/common.rb:262)"