Docstring of time_delta argument minimum_unit conflicts with implementation

[mjpieters]

The docstring for time_delta() says this about the minimum_unit argument:

        minimum_unit: The lowest unit that can be used. Options: "years", "months",
            "days", "hours", "minutes", "seconds", "milliseconds" or "microseconds".

but the implementation will raise an exception if you try to use any value larger than "seconds":

    tmp = Unit[minimum_unit.upper()]
    if tmp not in (Unit.SECONDS, Unit.MILLISECONDS, Unit.MICROSECONDS):
        raise ValueError(f"Minimum unit '{minimum_unit}' not supported")

Either update the docstring to only mention the last three options, or update the code to support the other units too.