Fix mypy ci

[nateraw]

Seeing if pinning version of mypy to previous version fixes CI

[HuggingFaceDocBuilderDev]

The documentation is not available anymore as the PR was closed or merged.

[nateraw]

Oh by the way, I did find that by changing these two signatures in _deprecation.py, you can get mypy to pass as well on latest version...

# added 'list'
class DeprecateListMetaclass(type, list):

# added 'type'
class DeprecatedList(list, type, metaclass=DeprecateListMetaclass):

Though I have no idea what I'm doing here or if this is OK 😅

[nateraw]

the other option is to just ignore the errors for that class or file

[Wauplin]

Thanks @nateraw for having a look at it :) I just played locally with mypy and doesn't really understand the class DeprecatedList(list, type, metaclass=DeprecateListMetaclass): solution either. Since it's very specific (and will be removed in a few versions), I would keep it as it is now. Besides, I already check in the metaclass init if the base is a subtype of list (which mypy would guarantee) so really not necessary to think too much about it IMO.

Let's pin the mypy version, it's good practice anyway :)