[FLINK-13519] [docs] Rewrite Elasticsearch 6.x example for Scala to use RuntimeContext and RequestIndexer

[a-romero]

What is the purpose of the change

Rewrite Elasticsearch 6.x example for Scala to use RuntimeContext and RequestIndexer

Brief change log

The Scala example in the documentation for the Elasticsearch Connector, version 6.x, will not build. The class ElasticsearchSinkFunction[String] requires a RuntimeContext and a RequestIndexer, which the example omits.

Also, type needs to be in inverse quotes as it's a Scala keyword.

new ElasticsearchSinkFunction[String] {
    def process(element: String, ctx: RuntimeContext, indexer: RequestIndexer) {
    ...
    val rqst: IndexRequest = Requests.indexRequest
        .index("my-index")
        .`type`("my-type")
        .source(json)

    indexer.add(rqst)
    }
}

Verifying this change

This change is a trivial rework / code cleanup without any test coverage.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: no
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Yarn/Mesos, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? not applicable

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Automated Checks

Last check on commit e7fe8ef (Thu Oct 24 18:04:45 UTC 2019)

Warnings:

• Documentation files were touched, but no .zh.md files: Update Chinese documentation or file Jira ticket.

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CI report:

• e7fe8ef : SUCCESS Build

[a-romero]

Hi @rmetzger , just wondering if this is ok to merge now?

[zentol]

Suggested change

	val esSinkBuilder = new ElasticsearchSink.Builer[String](
	val esSinkBuilder = new ElasticsearchSink.Builder[String](