[Doc][Logstash]: Update logstash doc to reflect the latest plugin (#542)
[Doc][Logstash]: Update logstash doc to reflect the latest plugin (#542)

Documents latest changes to Logstash datadog plugin
DataDog/integrations-extras,DataDog/integrations-extras,DataDog/integrations-extras,DataDog/integrations-extras,DataDog/integrations-extras