Fix demos for CPU inference

I tried running both the HF and the local demo on a computer without a GPU, and ran into `AssertionError: Torch not compiled with CUDA enabled` These were the problem areas I fixed: * HF demo * `torch.cuda.get_device_properties` will fail if `torch.cuda.is_available()` is `False` * Local demo * `torch.cuda.get_device_properties` will fail if `torch.cuda.is_available()` is `False` * `torch.autocast` did not have the correct device passed in * The Grounding DINO `predict(` did not pass in a value for the `device` argument, which is `cuda` by default