Align indices options of auto-configured ReactiveElasticsearchTemplate with Spring Data Elasticsearch's default

[wilkinsona]

See #30096 for background.

Our auto-configured ReactiveElasticsearchTemplate configures indices options to strictExpandOpenAndForbidClosed but Spring Data Elasticsearch uses strictExpandOpenAndForbidClosedIgnoreThrottled by default. We should remove our configuration of the indices options so that we align with Spring Data Elasticsearch. As this is potentially a breaking change, we'll do it in 2.7.x and mention it in the release notes.

Until we tackle #30379, users that want to keep the current behaviour can define their own bean:

@Bean
ReactiveElasticsearchTemplate reactiveElasticsearchTemplate(ReactiveElasticsearchClient client, ElasticsearchConverter converter) {
    ReactiveElasticsearchTemplate template = new ReactiveElasticsearchTemplate(client, converter);
    template.setIndicesOptions(IndicesOptions.strictExpandOpenAndForbidClosed());
    return template;
}