Remove `jupyter-contrib-nbextensions` from install requirements

[dogganon]

From its project description:

Due to major differences between the Jupyter Notebook and JupyterLab, the extensions in this repository will not work in JupyterLab.

Bundling jupyter-contrib-nbextensions with the package breaks jupyter-nbconvert under JupyterLab 4. This is unacceptable. Old jupyter extensions like this should be avoided at all costs. Besides, I don't see jupyter-contrib-nbextensions being used in this project anywhere other than a troubleshooting guide which presumably only applies to JupyterLab < 3.

Therefore, I propose that jupyter-contrib-nbextensions be:

• Either completely removed from the install requirements
• Or made optional

[prabhakk-mw]

@chen1682-ntu-edu-sg , Thank you for reporting this issue!
We've updated our repository to remove its dependency on this package.