[PROPOSAL] Release 2.9.0

[vibrantvarun]

What/Why
What are you proposing?
In a few sentences, describe the feature and its core capabilities.
If possible, can we release 2.9.0 with #857 as it is a change that would enable a new feature for our customers.

Is that an alright process to go through? @dblock @VachaShah

[vibrantvarun]

cc: @vamshin

[VachaShah]

2.9.0 is released: https://repo1.maven.org/maven2/org/opensearch/client/opensearch-java/2.9.0/

https://github.com/opensearch-project/opensearch-java/releases/tag/v2.9.0