The current link for "Java 23: Key Concepts in Brief — Sergio Petrucci" (https://petrucci.dev/java23.html) loads a blank page. The Wayback Machine has a working capture:



https://web.archive.org/web/20241213171851/https://petrucci.dev/java23.html



This PR updates the entry in books/free-programming-books-langs.md to point to the archived page and adds a short note indicating the original page currently shows blank.



Verified the Wayback capture on 2025-10-30. Fixes #12315.



