add changelog entry

Author: donoghuc

CHANGELOG.md

@@ -1,3 +1,6 @@
+## Unreleased
+  - Include httpclient5/httpcore5 from the `elasticsearch-java` artifact [#455](https://github.com/elastic/logstash-filter-elastic_integration/pull/455)
+
 ## 9.4.1
   - Upgrades `tools.jackson.core` dependency to 3.1.1 [#454](https://github.com/elastic/logstash-filter-elastic_integration/pull/454)