Adjectives.txt missing from wheel

Hi,



I just built a docker image using the latest Jupyter and when I try to open a notebook see the error



```

   File "/usr/local/lib/python3.8/site-packages/nbformat/corpus/words.py", line 15, in acceptable_adjectives

   with open(os.path.join(os.path.dirname(__file__), 'adjectives.txt'), 'r') as adjectives_file:

   FileNotFoundError: [Errno 2] No such file or directory: '/usr/local/lib/python3.8/site-packages/nbformat/corpus/adjectives.txt'

```



Looking at nbformat-5.0.9b0-py3-none-any.whl from PyPi (https://files.pythonhosted.org/packages/20/4a/bef9724bf4682c42f729d753a1c9ff5b9db97f64d155e5b3cd1a9bd21a60/nbformat-5.0.9b0-py3-none-any.whl) that file is indeed missing:



```

> unzip -l nbformat-5.0.9b0-py3-none-any.whl

Archive:  nbformat-5.0.9b0-py3-none-any.whl

  Length      Date    Time    Name

---------  ---------- -----   ----

     4962  2020-12-20 23:09   nbformat/__init__.py

      342  2020-12-20 23:09   nbformat/_compat.py

      122  2020-12-20 23:09   nbformat/_version.py

     2074  2020-12-20 23:09   nbformat/converter.py

     5353  2020-12-20 23:09   nbformat/current.py

     2547  2020-12-20 23:09   nbformat/json_compat.py

     1709  2020-12-20 23:09   nbformat/notebooknode.py

     2088  2020-12-20 23:09   nbformat/reader.py

      421  2020-12-20 23:09   nbformat/sentinel.py

    20454  2020-12-20 23:09   nbformat/sign.py

    11191  2020-12-20 23:09   nbformat/validator.py

        0  2020-12-20 23:09   nbformat/corpus/__init__.py

      608  2020-12-20 23:09   nbformat/corpus/words.py

        0  2020-12-20 23:09   nbformat/corpus/tests/__init__.py

...

```



(It is present in the tarball, and setup.py looks fine to me).



Sorry if I am doing something dumb, but this looks like a bug?  Particularly since this was released yesterday?



Cheers,

Andrew



Edit: I should add, sorry, that my docker image has:



```

 cat _version.py 

# Make sure to update package.json, too!

version_info = (5, 0, 9, 'beta0')

__version__ = '.'.join(map(str, version_info))

```

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