Correct the version number

Author: adamgraham

README.md

@@ -4,7 +4,7 @@
 
 - **Difficulty**: Intermediate
 - **Topics**: Multi-directional Shooting, Random Generation
-- **Version**: Unity 2019.4 LTS
+- **Version**: Unity 2020.2
 - **Author**: [@adamgraham](https://github.com/adamgraham)
 - [**Tutorial Video**](https://youtu.be/cIeWhztKyAg)
 - [**Source Code**](https://github.com/zigurous/unity-asteroids-tutorial)