[Issue][Logstash] Link to a non available service (http://grokdebug.herokuapp.com)

[alexandrechevalier]

Type of issue

Inaccurate

What documentation page is affected

https://www.elastic.co/docs/reference/logstash/plugins/plugins-filters-grok

What happened?

The app http://grokdebug.herokuapp.com/ is no longer available

Additional info

No response