Update examples using updated bulk (available in 9.3.1)

:warning: Breaking Change: elasticsearch.bulk Step
The elasticsearch.bulk step now properly supports all bulk operations (index, create, update, delete) and follows the official Elasticsearch bulk API format.

It's already in main and will be backported to 9.3.1.

## What changed:
Previously, documents were auto-wrapped with { index: {} }. Now you must explicitly specify the action for each document.

## Migration required:
### Before:
operations:
- name: "Yellowstone"
category: "geothermal"
- name: "Grand Canyon"
category: "canyon"
### After:
operations:
- create: {}
- name: "Yellowstone"
category: "geothermal"
- create: {}
- name: "Grand Canyon"
category: "canyon"

## New capabilities:
All bulk operations now work: create, index, update, delete
refresh parameter now works correctly
Update operations with _id and doc fields supported