Update to v7.9.2

.env

-ELK_VERSION=7.9.1
+ELK_VERSION=7.9.2

README.md

 # Elastic stack (ELK) on Docker
 
 [![Join the chat at https://gitter.im/deviantony/docker-elk](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/deviantony/docker-elk?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
-[![Elastic Stack version](https://img.shields.io/badge/ELK-7.9.1-blue.svg?style=flat)](https://github.com/deviantony/docker-elk/issues/529)
+[![Elastic Stack version](https://img.shields.io/badge/ELK-7.9.2-blue.svg?style=flat)](https://github.com/deviantony/docker-elk/issues/539)
 [![Build Status](https://api.travis-ci.org/deviantony/docker-elk.svg?branch=master)](https://travis-ci.org/deviantony/docker-elk)
 
 Run the latest version of the [Elastic stack][elk-stack] with Docker and Docker Compose.
@@ -239,7 +239,7 @@ Create an index pattern via the Kibana API:
 ```console
 $ curl -XPOST -D- 'http://localhost:5601/api/saved_objects/index-pattern' \
     -H 'Content-Type: application/json' \
-    -H 'kbn-version: 7.9.1' \
+    -H 'kbn-version: 7.9.2' \
     -u elastic:<your generated elastic password> \
     -d '{"attributes":{"title":"logstash-*","timeFieldName":"@timestamp"}}'
 ```

docker-stack.yml

@@ -3,7 +3,7 @@ version: '3.3'
 services:
 
   elasticsearch:
-    image: docker.elastic.co/elasticsearch/elasticsearch:7.9.1
+    image: docker.elastic.co/elasticsearch/elasticsearch:7.9.2
     ports:
       - "9200:9200"
       - "9300:9300"
@@ -23,7 +23,7 @@ services:
       replicas: 1
 
   logstash:
-    image: docker.elastic.co/logstash/logstash:7.9.1
+    image: docker.elastic.co/logstash/logstash:7.9.2
     ports:
       - "5000:5000"
       - "9600:9600"
@@ -41,7 +41,7 @@ services:
       replicas: 1
 
   kibana:
-    image: docker.elastic.co/kibana/kibana:7.9.1
+    image: docker.elastic.co/kibana/kibana:7.9.2
     ports:
       - "5601:5601"
     configs: