fix(dispatcher): explicitly disable exception chaining

[lengau]

In these cases, the chaining doesn't provide useful additional data.

Drive-by: updates ruff to 0.2

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[lengau]

@mr-cal This does change the traceback, since it sets the __context__ to None rather than the previous exception. However, the context exceptions aren't useful to either an end user or a developer using this library since they're implementation details (they're mostly KeyError in places where we use dictionaries and in one case a StopIteration where we call next()). In all cases, these are raising ArgumentParsingError, which the application should always catch and display (but should never care about context).