Update ELK images
elasticsearch:
- https://github.com/docker-library/elasticsearch/commit/e309ccf: Update to 6.8.4
- https://github.com/docker-library/elasticsearch/commit/5816ba1: Update to 7.4.1
logstash:
- https://github.com/docker-library/logstash/commit/034ec4e: Update to 6.8.4
- https://github.com/docker-library/logstash/commit/338bfda: Update to 7.4.1
kibana:
- https://github.com/docker-library/kibana/commit/f59b7cc: Update to 6.8.4
- https://github.com/docker-library/kibana/commit/b5c76d5: Update to 7.4.1
Docker Library Bot