Use torchcodec lowercase for wheel names

[NicolasHug]

This PR renames our wheel files from TorchCodec to torchcodec.

As I published 0.2.1 I received the following email from PyPI:

This email is notifying you of an upcoming deprecation that we have determined may affect you as a result of your recent upload to 'TorchCodec'.
In the future, PyPI will require all newly uploaded binary distribution filenames to comply with the binary distribution format. Any binary distributions already uploaded will remain in place as-is and do not need to be updated.
Specifically, your recent upload of 'TorchCodec-0.2.1-cp39-cp39-macosx_11_0_arm64.whl' is incompatible with the distribution format specification because the filename does not contain the normalized project name 'torchcodec'.