Remove unused configuration from pyproject.toml

[antonwolfy]

The PR removes pytest configuration from pyproject.toml since it was never used due to invalid name used tool.pytest.ini.options which never supported by pytest.

The latest pytest warns about that explicitly:

PytestConfigWarning: Unknown config option: ini

since the correct name is tool.pytest.ini_options.

The configuration might be returned back to pyproject.toml when really needed.

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[github-actions]

View rendered docs @ https://intelpython.github.io/dpnp/pull/2729/index.html

[github-actions]

Array API standard conformance tests for dpnp=0.20.0dev1=py313h509198e_52 ran successfully.
Passed: 1227
Failed: 0
Skipped: 9

[coveralls]

coverage: 81.304%. remained the same
when pulling d06c5f6 on remove-unused-config
into 7b73f74 on master.