Stop loading nav-toc.js to restore Material native nav interaction

[abn2357]

Summary

• Remove javascripts/nav-toc.js from extra_javascript in mkdocs.yml so the left navigation falls back to Material's native interaction behavior, since the TOC is no longer integrated into the nav.
• The nav-toc.js file itself is intentionally kept in the repo to make it easy to re-enable TOC-into-nav integration in the future if needed.

Test plan

• Build the site locally and confirm the left navigation behaves as expected (Material default interaction).
• Verify no console errors related to the removed script.