Always return a real dtype from dpnp.linalg.cond

[antonwolfy]

The PR updates dpnp.linalg.cond implementation to always return an array of real dtype, because the condition number can't be complex.

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[github-actions]

View rendered docs @ https://intelpython.github.io/dpnp/index.html

[github-actions]

Array API standard conformance tests for dpnp=0.19.0dev3=py313h509198e_8 ran successfully.
Passed: 1227
Failed: 0
Skipped: 9

[coveralls]

coverage: 72.108%. remained the same
when pulling f69b9d5 on correct-linalg-cond-dtype
into 54ee640 on master.

[vtavana]

Thank you, @antonwolfy!