update README

Author: martinescardo

HoTT/README.md

@@ -2,7 +2,7 @@
 
  * [HoTT Lecture 1](HoTTEST_Lecture_1.pdf) ([Paige North](https://paigenorth.github.io/))
  * [HoTT Lecture 2](HoTTEST_Lecture_2.pdf) ([Paige North](https://paigenorth.github.io/))
- * [HoTT Lecture 3](HoTTEST_Lecture_2.pdf) ([Paige North](https://paigenorth.github.io/))
+ * [HoTT Lecture 3](HoTTEST_Lecture_3.pdf) ([Paige North](https://paigenorth.github.io/))
  * [Worksheets](Worksheets/)
  * [Lecture Q&A](Q-and-A/)