TASK: Update travis config to use ES 7.6

Author: daniellienert

.travis.yml

@@ -22,7 +22,7 @@ before_install:
   - export NEOS_TARGET_VERSION=5.1
   - cd ..
   - if [ "$ES" = 6 ]; then wget --no-check-certificate https://artifacts.elastic.co/downloads/elasticsearch/elasticsearch-6.8.6.tar.gz && tar xvfz elasticsearch-6.8.6.tar.gz && mv elasticsearch-6.8.6 elasticsearch; fi
-  - if [ "$ES" = 7 ]; then wget --no-check-certificate https://artifacts.elastic.co/downloads/elasticsearch/elasticsearch-7.5.2-linux-x86_64.tar.gz && tar xvfz elasticsearch-7.5.2-linux-x86_64.tar.gz && mv elasticsearch-7.5.2 elasticsearch; fi
+  - if [ "$ES" = 7 ]; then wget --no-check-certificate https://artifacts.elastic.co/downloads/elasticsearch/elasticsearch-7.6.0-linux-x86_64.tar.gz && tar xvfz elasticsearch-7.6.0-linux-x86_64.tar.gz && mv elasticsearch-7.6.0 elasticsearch; fi
   - cd elasticsearch
   - bin/elasticsearch -d
   - cd ..