[DOC] Update documentation for opensearch-php 2.4.0+

[dblock]

What do you want to do?

• [x] Request a change to existing documentation
• [ ] Add new documentation
• [ ] Report a technical problem with the documentation
• [ ] Other

Coming from https://github.com/opensearch-project/opensearch-php/issues/283#issuecomment-2636370141, the documentation on opensearch.org in https://opensearch.org/docs/latest/clients/php/#connecting-to-opensearch now recommends a deprecated way of making connections with the php client and needs to be updated.

[krisfreedain]

Catch All Triage - 1 2

[natebower]

@kolchfa-aws

[kolchfa-aws]

Closing in favor of #10007