[BSC AIF AP] Remove bonus challenge notebooks

[krishnakalyan3]

Summary

• Remove the bonus challenge notebooks from tutorial/jupyter_notebook/bonus_challenge
• Remove bonus challenge links from notebook navigation and the tutorial start page

Verification

• rg -n "bonus_challenge|07_bonus_challenge|Bonus Challenge|Bonus challenge|bonus challenge" tutorial/start_here.ipynb tutorial/jupyter_notebook --glob '*.ipynb' returned no matches
• jq empty tutorial/start_here.ipynb tutorial/jupyter_notebook/*.ipynb