Adjust --timeout default to 1

The definition of the --timeout argument indicates the type is int, but the default was None. This fix aligns the default's type.

(Granted, there's no reason to prevent different types for argument default/value in general—the type parameter for add_argument() is really a conversion function and not actually a type specification. But in this case there's no benefit to having a default of None and the change makes the intent more clear.)

Fixes: 4046e06c ("run: Option to override default 1 day timeout")