Add k type check to triu_indices

[antonwolfy]

The PR adds explicit type check to k keyword in dpnp.triu_indices function.

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[github-actions]

View rendered docs @ https://intelpython.github.io/dpnp/pull/2855/index.html

[coveralls]

coverage: 78.431% (+0.004%) from 78.427% — add-k-type-check-to-triu_indices into master

[github-actions]

Array API standard conformance tests for dpnp=0.20.0dev6=py313h509198e_16 ran successfully.
Passed: 1357
Failed: 3
Skipped: 16

[vlad-perevezentsev]

LGTM
Thank you @antonwolfy