Replace internal colab links with aliyun links

[jerlich]

Any links in the notebooks which point to colab need to be replaced with the appropriate China accessible link.

I think the easiest way to to just search and replace. Since we will use the same directory structure , it should be as easy as running a find/replace on the whole repository.

[jerlich]

@superr90 seems like this can be done with a single sed command on the repo.