Remove link to course materials

These cannot be accessed without UNSW credentials.

docs/community/training/debugging/resources.md

@@ -5,6 +5,5 @@
     - [Debugging stories](https://jvns.ca/#debugging-stories)
     - [The Pocket Guide to Debugging](https://jvns.ca/blog/2022/12/21/new-zine--the-pocket-guide-to-debugging/) (see the [table of contents](https://jvns.ca/images/debugging-guide-toc.png))
     - [Notes on building debugging puzzles](https://jvns.ca/blog/2021/04/16/notes-on-debugging-puzzles/)
-- [Learn Debugging](https://www.cse.unsw.edu.au/~learn/debugging/)
 - [Debug with pdb and breakpoint](https://hamatti.org/posts/debug-with-pdb-and-breakpoint/)
 - [Advanced R: Debugging](https://adv-r.hadley.nz/debugging.html)