.travis.yml in search_flip-3.0.0.beta3 vs .travis.yml in search_flip-3.0.0.beta4

- old
+ new

@@ -3,10 +3,10 @@
 env:
   - ES_IMAGE=plainpicture/elasticsearch:2.4.1_delete-by-query
   - ES_IMAGE=elasticsearch:5.4
   - ES_IMAGE=docker.elastic.co/elasticsearch/elasticsearch:6.7.0
   - ES_IMAGE=docker.elastic.co/elasticsearch/elasticsearch:7.0.0
-  - ES_IMAGE=docker.elastic.co/elasticsearch/elasticsearch:7.4.0
+  - ES_IMAGE=docker.elastic.co/elasticsearch/elasticsearch:7.6.0
 rvm:
   - ruby-2.6.2
 before_install:
   - docker-compose up -d
   - sleep 10