DEPR: depreecate uppercase units 'MIN', 'MS', 'US', 'NS' in Timedelta and 'to_timedelta'
Deprecated uppercase strings `“MIN”, “MS”, “US”, “NS”` denoting units from the class `Timedelta` and the method `to_timedelta`.

The reason: for period/offsets these strings are already deprecated. Instead of the uppercase strings we use lowercase: `“min”, “ms”, “us”, “ns”`.
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