Trying to convert Float8_e4m3fn to the MPS backend but it does not have support for that dtype.

### Custom Node Testing

- [x] I have tried disabling custom nodes and the issue persists (see [how to disable custom nodes](https://docs.comfy.org/troubleshooting/custom-node-issues#step-1%3A-test-with-all-custom-nodes-disabled) if you need help)

### Expected Behavior

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### Actual Behavior

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### Steps to Reproduce

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### Debug Logs

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### Other

_No response_