binder-examples/jupyter-extension binder links do not launch

[nathanweeks]

Bug description

The binder links in https://github.com/binder-examples/jupyter-extension do not successfully launch in either JupyterLab or Jupyter Notebook mode. The following image build error is reported:

Enabling notebook extension jupyter-js-widgets/extension...
      - Validating: OK
An error occurred.
ValueError: 
"@jupyter-widgets/[email protected]" is not compatible with the current JupyterLab
Conflicting Dependencies:
JupyterLab                        Extension      Package
>=3.2.8 <3.3.0                    >=0.19.1 <0.20.0@jupyterlab/application
>=5.2.8 <5.3.0                    >=2.0.0 <3.0.0 @jupyterlab/coreutils
>=3.2.8 <3.3.0                    >=0.19.1 <0.20.0@jupyterlab/notebook
>=3.2.8 <3.3.0                    >=0.19.1 <0.20.0@jupyterlab/rendermime
>=3.2.8 <3.3.0                    >=1.1.0 <2.0.0 @jupyterlab/rendermime-interfaces
>=6.2.8 <6.3.0                    >=3.0.0 <4.0.0 @jupyterlab/services
See the log file for details:  /tmp/jupyterlab-debug-pkro1jpp.log

How to reproduce

Jupyter Notebook link: https://beta.mybinder.org/v2/gh/binder-examples/jupyter-extension/HEAD?urlpath=/tree/index.ipynb

JupyterLab link: https://beta.mybinder.org/v2/gh/binder-examples/jupyter-extension/HEAD?urlpath=lab/tree/index.ipynb

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