gh-143089: Fix ParamSpec default examples to use list instead of tuple

[VanshAgarwal24036]

This PR fixes incorrect ParamSpec default examples in the ParamSpec
docstring shown by help(ParamSpec).

According to the typing specification, ParamSpec defaults must be a list
literal, ellipsis (...), or another ParamSpec. Tuples are not permitted.

The docstring examples previously used tuple defaults. These are updated
to use list defaults to match the typing specification and the existing
documentation.

Closes: gh-143089

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[python-cla-bot]

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[sobolevn]

There's another case of default=() in test_paramspec, please fix it as well.

[sobolevn]

No news entry is required for this change, please remove it.

[VanshAgarwal24036]

Thanks for the review! I updated the remaining default=() case in the test and removed the NEWS entry as requested.

[VanshAgarwal24036]

Thanks again! I initially changed the default=() in the test, but CI showed that the runtime default value is still expected to be a tuple.
I have now reverted the test change so behavior remains unchanged and only the examples/docs use lists.

[picnixz]

Actually why didn't you update the test?

Tests were not changed

[VanshAgarwal24036]

I originally updated the test, but reverted it after CI showed that the runtime default is still expected to be a tuple. So only the docs/examples now use list syntax.

[picnixz]

Mmmh, should we actually enforce it at runtime then? maybe as a follow-up PR? cc @JelleZijlstra