[Task]: Deprecate runner for Spark v2

What needs to happen?

It is time to deprecate the Spark 2 runner in Beam, see this discussion. Databricks is also dropping support for runtimes using Spark 2 by the end of June 2022.

With that the Spark 3 runner will become the default and only Spark runner.

Issue Priority

Priority: 2

Issue Component

Component: runner-spark