Remove Wisconsin list since it is 404

Author: rxin

README.md

@@ -107,5 +107,4 @@ A number of schools have their own reading lists for graduate students in databa
 * Berkeley [PhD prelim exam reading list](http://www.eecs.berkeley.edu/GradAffairs/CS/Prelims/db.html) and [CS286 grad database class reading list](http://www.cs286.net/home/reading-list)
 * [Brown CSCI 2270 Advanced Topics in Database Management](http://www.cs.brown.edu/courses/cs227/papers.html)
 * [Stanford PhD qualifying exam](http://infolab.stanford.edu/db_pages/infoqual.html)
-* [Wisconsin](http://www.cs.wisc.edu/sites/default/files/db.reading.pdf)
 * MIT: [Database Systems 6.830 year 2014](http://db.csail.mit.edu/6.830/sched.html) and [year 2010](http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-830-database-systems-fall-2010/readings/)