Upgrade the Elasticsearch version

[ChrisHegarty]

The current version of Elasticsearch used in this benchmark is version 8.7.0. While there are many enhancements to functionality in more modern versions, there are specific improvements to low-level performance of vector comparison operations that greatly affect the performance of vector search - namely the use of SIMD to optimise the vector ops.

[ChrisHegarty]

At time of writing, the most recent version is:
https://artifacts.elastic.co/downloads/elasticsearch/elasticsearch-9.0.2-linux-x86_64.tar.gz

Care should be taken in the docker file when customising the JVM options, since replacing it may drastically affect how Elasticsearch performs. It is best to add custom setting in jvm.options.d (rather than jvm.options).
https://www.elastic.co/docs/reference/elasticsearch/jvm-settings#set-jvm-options

I'm happy to help with this.