fleet_context docs update (#13221)
- **Description:** Changed the fleet_context documentation to use
`context.download_embeddings()` from the latest release from our
package. More details here:
https://github.com/fleet-ai/context/tree/main#api
- **Issue:** n/a
- **Dependencies:** n/a
- **Tag maintainer:** @baskaryan
- **Twitter handle:** @andrewthezhou
