Fix inference_tutorial notebook

[amrzv]

Hi.

• fixed ModuleNotFoundError while running inference_tutorial.ipynb notebook
• removed unnecessary imports os, torch.nn.functional, matplotlib.image;
• fixed referenced to CONTRIBUTING, LICENCE, NOTICE, CODE_OF_CONDUCT inside {omnivore,omnimae}/README.md

P.S: during this import from torchvision.transforms._transforms_video import NormalizeVideo a UserWarning raised:

so probably it's better to fix this import for future.

P.S.S: tested in colab environment, "Run all cells" without any errors.