mlx - add argpartition to numpy

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes are missing coverage. Please review.

:exclamation: No coverage uploaded for pull request base (mlx@ad948c2). Click here to learn what that means.

Files	Patch %	Lines
keras/src/backend/mlx/numpy.py	0.00%	3 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## mlx #19680 +/- ## ====================================== Coverage ? 75.54% ====================================== Files ? 508 Lines ? 47225 Branches ? 8686 ====================================== Hits ? 35675 Misses ? 9808 Partials ? 1742 ``` | [Flag](https://app.codecov.io/gh/keras-team/keras/pull/19680/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=keras-team) | Coverage Δ | | |---|---|---| | [keras](https://app.codecov.io/gh/keras-team/keras/pull/19680/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=keras-team) | `75.39% <0.00%> (?)` | | | [keras-jax](https://app.codecov.io/gh/keras-team/keras/pull/19680/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=keras-team) | `59.76% <0.00%> (?)` | | | [keras-numpy](https://app.codecov.io/gh/keras-team/keras/pull/19680/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=keras-team) | `54.31% <0.00%> (?)` | | | [keras-tensorflow](https://app.codecov.io/gh/keras-team/keras/pull/19680/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=keras-team) | `61.07% <0.00%> (?)` | | | [keras-torch](https://app.codecov.io/gh/keras-team/keras/pull/19680/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=keras-team) | `59.78% <0.00%> (?)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=keras-team#carryforward-flags-in-the-pull-request-comment) to find out more.

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.