Register Magistral Presets to Hub

[laxmareddyp]

Description of the change

Reference

Colab Notebook

Checklist

• I have added all the necessary unit tests for my change.
• I have verified that my change does not break existing code and works with all backends (TensorFlow, JAX, and PyTorch).
• My PR is based on the latest changes of the main branch (if unsure, rebase the code).
• I have followed the Keras Hub Model contribution guidelines in making these changes.
• I have followed the Keras Hub API design guidelines in making these changes.
• I have signed the Contributor License Agreement.

[gemini-code-assist]

Code Review

This pull request adds two new model presets to the Mistral model configuration. The review feedback correctly identifies a naming inconsistency where 'magistral' is used instead of 'mistral', which appears to be a typo or AI hallucination. The reviewer has provided a clear code suggestion to rename these presets to 'mistral_small' to align with repository standards.