[Docs] Reflect Spark 2 support removal with ElasticSearch 9

[ashish-b-choudhary-db]

The documentation states Deprecated in 9.0 - Support for Spark 2.x in elasticsearch-hadoop is deprecated.
While it's been completely removed from the library.

[masseyke]

That looks like a mistake in the documentation. Spark 2 was deprecated in 8.18.0 (#2305) and removed for 9.0 (#2316).