Still refers to "codex"

SimplePages refers to the "Omeka codex" with an outdated link.

http://omeka.org/codex/Shortcodes

<img width="708" alt="Image" src="https://github.com/user-attachments/assets/ddb5bc35-33ab-4787-b256-85163da7e8c4" />

It's cute, and the link redirects correctly, but we may want to update that. 