Bump version.elasticsearch from 5.6.0 to 7.17.9 (#3029)

* Bump version.elasticsearch from 5.6.0 to 7.17.9

Bumps `version.elasticsearch` from 5.6.0 to 7.17.9.

Updates `elasticsearch-rest-client` from 5.6.0 to 7.17.9
- [Release notes](https://github.com/elastic/elasticsearch/releases)
- [Changelog](https://github.com/elastic/elasticsearch/blob/main/CHANGELOG.md)
- [Commits](elastic/elasticsearch@v5.6.0...v7.17.9)

Updates `elasticsearch-rest-high-level-client` from 5.6.0 to 7.17.9
- [Release notes](https://github.com/elastic/elasticsearch/releases)
- [Changelog](https://github.com/elastic/elasticsearch/blob/main/CHANGELOG.md)
- [Commits](elastic/elasticsearch@v5.6.0...v7.17.9)

---
updated-dependencies:
- dependency-name: org.elasticsearch.client:elasticsearch-rest-client
  dependency-type: direct:production
  update-type: version-update:semver-major
- dependency-name: org.elasticsearch.client:elasticsearch-rest-high-level-client
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

* keep older dep versions

---------

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Sylvain Juge <sylvain.juge@elastic.co>

Author: dependabot[bot]

apm-agent-plugins/apm-es-restclient-plugin/apm-es-restclient-plugin-7_x/pom.xml

@@ -12,7 +12,7 @@
     <name>${project.groupId}:${project.artifactId}</name>
 
     <properties>
-        <version.elasticsearch>7.17.6</version.elasticsearch>
+        <version.elasticsearch>7.17.9</version.elasticsearch>
         <apm-agent-parent.base.dir>${project.basedir}/../../..</apm-agent-parent.base.dir>
     </properties>