Fixed a link to LLNL tutorials (#3521)

free-programming-books.md

@@ -674,7 +674,7 @@
 #### Parallel Programming
 
 * [High Performance Computing](http://cnx.org/contents/bb821554-7f76-44b1-89e7-8a2a759d1347%405.2) - Charles Severance & Kevin Dowd (PDF, ePUB)
-* [High Performance Computing Training](https://computing.llnl.gov/?set=training&page=index) (LLNL materials)
+* [High Performance Computing Training](https://web.archive.org/web/20170702124132/https://hpc.llnl.gov/training/tutorials) (LLNL materials)
 * [High-Performance Scientific Computing](https://andreask.cs.illinois.edu/Teaching/HPCFall2012) (class lectures and slides)
 * [Introduction to High-Performance Scientific Computing](http://pages.tacc.utexas.edu/~eijkhout/istc/istc.html) - Victor Eijkhout
 * [Introduction to Parallel Computing](https://computing.llnl.gov/tutorials/parallel_comp/) - Blaise Barney