Reference to private repository

[ePirat]

There is a submodule pointing to https://github.com/AOMediaCodec/oar-private (a private repo) which means that main can't be built because the submodule can't be fetched.

[yilun-zhangs]

Hi @ePirat
The latest libiamf is for v2.0, but the 2.0 spec is not released yet, and it depends on the oar which is not opened as well.
Once it is public, we will replace the private repository with public one.

Thanks