Bump elasticsearch from 2.4.3 to 6.8.17

Bumps [elasticsearch](https://github.com/elastic/elasticsearch) from 2.4.3 to 6.8.17.
- [Release notes](https://github.com/elastic/elasticsearch/releases)
- [Commits](elastic/elasticsearch@v2.4.3...v6.8.17)

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

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

pom.xml

@@ -142,7 +142,7 @@
                 <dependency>
                     <groupId>org.elasticsearch</groupId>
                     <artifactId>elasticsearch</artifactId>
-                    <version>2.4.3</version>
+                    <version>6.8.17</version>
                     <scope>provided</scope>
                 </dependency>
             </dependencies>
@@ -156,7 +156,7 @@
                 <dependency>
                     <groupId>org.elasticsearch</groupId>
                     <artifactId>elasticsearch</artifactId>
-                    <version>5.6.16</version>
+                    <version>6.8.17</version>
                     <scope>provided</scope>
                 </dependency>
                 <dependency>
@@ -188,7 +188,7 @@
                 <dependency>
                     <groupId>org.elasticsearch</groupId>
                     <artifactId>elasticsearch</artifactId>
-                    <version>6.0.1</version>
+                    <version>6.8.17</version>
                     <scope>provided</scope>
                 </dependency>
                 <dependency>
@@ -220,7 +220,7 @@
                 <dependency>
                     <groupId>org.elasticsearch</groupId>
                     <artifactId>elasticsearch</artifactId>
-                    <version>6.8.10</version>
+                    <version>6.8.17</version>
                     <scope>provided</scope>
                 </dependency>
                 <dependency>
@@ -252,7 +252,7 @@
                 <dependency>
                     <groupId>org.elasticsearch</groupId>
                     <artifactId>elasticsearch</artifactId>
-                    <version>7.9.0</version>
+                    <version>6.8.17</version>
                     <scope>provided</scope>
                 </dependency>
                 <dependency>