.travis.yml in search_flip-3.1.0 vs .travis.yml in search_flip-3.1.1

- 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:7.6.0
+  - ES_IMAGE=docker.elastic.co/elasticsearch/elasticsearch:7.8.0
 rvm:
   - ruby-2.5.3
   - ruby-2.6.2
   - ruby-2.7.1
 before_install: