Bump elasticsearch from 5.5.2 to 6.8.17

Bumps [elasticsearch](https://github.com/elastic/elasticsearch) from 5.5.2 to 6.8.17.
- [Release notes](https://github.com/elastic/elasticsearch/releases)
- [Changelog](https://github.com/elastic/elasticsearch/blob/master/CHANGELOG.md)
- [Commits](https://github.com/elastic/elasticsearch/compare/v5.5.2...v6.8.17)

---
updated-dependencies:
- dependency-name: org.elasticsearch:elasticsearch
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>
diff --git a/pom.xml b/pom.xml
index 8ddff19..f4c122e 100644
--- a/pom.xml
+++ b/pom.xml
@@ -43,7 +43,7 @@
 
   <!-- Move these to the parent pom, when I create a parent pom -->
   <properties>
-    <elasticsearch.version>5.5.2</elasticsearch.version>
+    <elasticsearch.version>6.8.17</elasticsearch.version>
     <junit.version>4.8.2</junit.version>
     <log4j.version>1.2.16</log4j.version>
     <httpcomponent.version>4.4.1</httpcomponent.version>