Updated FE protocol spec link in README.md. (#294)

# Changes
- Updated the Fusion Engine spec link in the README file

README.md

@@ -8,7 +8,7 @@ This library provides message definitions and support functionality for interact
 time, as well as processing recorded output data. Both C++ and Python are supported.
 
 Click here to download the latest FusionEngine protocol specification PDF:
-[Point One FusionEngine Message Specification](http://pointonenav.com/files/fusion-engine-message-spec)
+[Point One FusionEngine Message Specification](https://pointonenav.com/wp-content/uploads/2023/11/FusionEngine-Message-Specification-v0.20.pdf)  
 
 See http://docs.pointonenav.com/fusion-engine/ for the latest C++ API documentation.