Update: Oberon : Algorithms and Data-Structures (#3286)

link to more up to date version with better font

old: http://www.ethoberon.ethz.ch/WirthPubl/AD.pdf
new: https://inf.ethz.ch/personal/wirth/AD.pdf

free-programming-books.md

@@ -1886,7 +1886,7 @@ Kerridge (PDF) (email address *requested*, not required)
 
 ### Oberon
 
-* [Algorithms and Data-Structures](http://www.ethoberon.ethz.ch/WirthPubl/AD.pdf) - Niklaus Wirth (PDF)
+* [Algorithms and Data-Structures](https://inf.ethz.ch/personal/wirth/AD.pdf) - Niklaus Wirth (PDF)
 * [Object-Oriented Programming in Oberon-2](http://ssw.jku.at/Research/Books/Oberon2.pdf) - Hanspeter Mössenböck (PDF)
 * [Programming in Oberon](https://www.inf.ethz.ch/personal/wirth/ProgInOberonWR.pdf) - Niklaus Wirth (PDF)