x_ai: Fix `Model::from_id` for Grok 4 (#38930)

This PR fixes `x_ai::Model::from_id`, which was not properly handling
`grok-4`.

Release Notes:

- N/A
94fe862fb6Marshall Bowers committed on 9/26/2025, 3:49:14 AM· committed by GitHubparent4f91fab
1 file changedLine totals unavailable