TYP: `SetIndex` missing `None`?

[lucascolley]

In [1]: import array_api_strict as xp; import array_api_extra as xpx

In [2]: x = xp.asarray(0)

In [3]: x = xpx.at(x)[None].set(2); x
Out[3]: Array(2, dtype=array_api_strict.int64)

@crusaderky should

array-api-extra/src/array_api_extra/_lib/_utils/_typing.pyi

Lines 98 to 100 in 4781856

	SetIndex: TypeAlias = (
	int | slice | EllipsisType | Array | tuple[int | slice | EllipsisType | Array, ...]
	)

have None in the union? Or am I misunderstanding the at interface?

x-ref https://github.com/scipy/scipy/pull/25517/changes#r3493017024