incorrect docs: pd.NA ** 0 should return 1
`pd.NA ** 0` returns 1. which is correct, as far as I understand <sup>1</sup>
However, the [documents, line 832](https://dev.pandas.io/docs/user_guide/missing_data.html) incorrectly claims that `pd.NA ** 0` returns 0.

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<sup>1</sup> although one can ask if `NULL**0` should behave like `NAN**0`