Do something with undocumented `pass` in `GenericMethodWrapper._build_kwargs()`

A bare `pass` with no explanation isn't great if that condition is ever hit: https://github.com/DiamondLightSource/httomo/blob/3276af4c8445a2e4f37806e30c68ca350a014ee3/httomo/method_wrappers/generic.py#L248-L249

Putting something here instead of a `pass` would be best, but if that can't be done, documenting why there is a `pass` here would be useful for developers' understanding.