DepthRenderer method='median' is not differentiable

[gtangg12]

https://github.com/nerfstudio-project/nerfstudio/blob/702886b213a5942b64250b3c4dc632e62237a511/nerfstudio/model_components/renderers.py#L330

requires_grad=False while for expected its True

Seems like it will create a lot of "why is this not learning issues" downstream. Perhaps an improvement would be to raise a warning.