Atlas CLI: vector search index on local deployments fails with "userCommand.indexes[0].fields is required"

## What happened

Creating a vector search index on an Atlas local deployment with `atlas deployments search indexes create` fails with `Error: (UnknownError) "userCommand.indexes[0].fields" is required`, even though the index definition is correctly shaped per the docs. The CLI was sending the wrong payload shape for local deployments. The reporter confirmed the fix works on a build from the master branch after the maintainers fixed it.

## The fix that worked

Upgrade the Atlas CLI to a release newer than 1.29.0 — the maintainers fixed the payload shape for local-deployment vector search indexes right after this was reported, and the reporter confirmed it works on the fixed build. Keep the index definition as in the docs (`type: vectorSearch` with a `definition.fields` array); no JSON reshaping is needed on fixed versions.