gh-94757: Fix documentation to include possible Exception for datetime.timestamp()

[yourlefthandman]

The function _PyTime_localtime may raise the OSError exception for windows when the datetime overflows

• Issue: error in datetime.timestamp on windows #94757

[bedevere-bot]

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[Vinalti]

Seems legit

[pganssle]

I would be mildly inclined to catch the OSError and reraise it as something else, but I guess we can at least include it in the documentation for backports.