[FIX_BROKEN_LINKS_ROBERT_HARPER] fix broken link to Robert Harper's collections of research papers (#572)

README.md

@@ -98,7 +98,7 @@ We're looking for pull requests related to papers we should add, better organiza
 * [Readings in Distributed Systems](http://christophermeiklejohn.com/distributed/systems/2013/07/12/readings-in-distributed-systems.html)
 * [Gradual Typing Bibliography](http://samth.github.io/gradual-typing-bib/)
 * [Security Data Science Papers](http://www.covert.io/the-definitive-security-datascience-and-machinelearning-guide/)
-* [Research Papers from Robert Harper, Carnegie Mellon University](http://www.cs.cmu.edu/~rwh/papers.html)
+* [Research Papers from Robert Harper, Carnegie Mellon University](https://www.cs.cmu.edu/~rwh/papers/index.html)
 * [Lobste.rs tagged as PDF](https://lobste.rs/t/pdf)
 * [The Morning Paper](http://blog.acolyer.org/)