Exclude headers with SYCL kernels from the coverage report

[antonwolfy]

The PR excludes the headers files under backend/kernels/elementwise_functions from the coverage report, because there is no way to cover structures used inside the SYCL kernels.

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[github-actions]

Array API standard conformance tests for dpnp=0.20.0dev0=py313h509198e_19 ran successfully.
Passed: 1227
Failed: 0
Skipped: 9

[github-actions]

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

[coveralls]

coverage: 74.446% (+6.6%) from 67.845%
when pulling 3febb00 on exclude-kernels-headers-from-default-coverage
into 37db1c5 on master.

[vlad-perevezentsev]

LGTM!
Thank you @antonwolfy
A small suggestion for the next PR:
Could you also exclude dpnp/to_numba folder from the coverage report?

[antonwolfy]

Could you also exclude dpnp/to_numba folder from the coverage report?

I think the folder has to be removed at all. It can be done in the follow up PR.