[BUG] Update USER_GUIDE.md for v3.0.0

[eshgovil]

What is the bug?

Creating an Index section of the user guide is now outdated on main branch: client.indices.create now accepts keyword arguments only.

How can one reproduce the bug?

Spin up a new OpenSearch instance, run each step of the user guide.

What is the expected behavior?

Response from created index should be {'acknowledged': True, 'shards_acknowledged': True, 'index': 'test-index'}

What is your host/environment?

• MacBook Pro M1 Pro
• Locally hosted docker container with OpenSearch following this guide
• opensearch-py==3.0.0

Do you have any screenshots?

Do you have any additional context?

[bruceduhamel]

This affects various calls to IndicesClient, minimally including converting all arguments to keyword only for create, delete, exists and get_alias. Notably, the documentation remains out of date as of right now.

[eht16]

I'd like to add reindex() and tasks.get() to the party.