Bump elasticsearch from 6.2.2 to 6.8.17

Bumps [elasticsearch](https://github.com/elastic/elasticsearch) from 6.2.2 to 6.8.17.
- [Release notes](https://github.com/elastic/elasticsearch/releases)
- [Commits](elastic/elasticsearch@v6.2.2...v6.8.17)

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

Signed-off-by: dependabot[bot] <[email protected]>

pom.xml

@@ -79,7 +79,7 @@
         <config.logger.fileappender.filename>${project.build.finalName}</config.logger.fileappender.filename>
         <version.java>1.8</version.java>
         <version.log4j>2.8.2</version.log4j>
-        <elasticsearch.version>6.2.2</elasticsearch.version>
+        <elasticsearch.version>6.8.17</elasticsearch.version>
     </properties>
 
     <profiles>