Merge pull request #199 from srobo/sr2021.9-sim

Update simulator link

Author: WillB97

simulator/index.md

@@ -38,7 +38,7 @@ a link to the package on [PyPI](https://pypi.org/).
 
 ### Installing the simulation
 
-1. [Download the simulation](https://github.com/srobo/competition-simulator/releases/download/sr2021.8/competition-simulator-sr2021.8.zip), and unzip it somewhere on your computer.
+1. [Download the simulation](https://github.com/srobo/competition-simulator/releases/download/sr2021.9/competition-simulator-sr2021.9.zip), and unzip it somewhere on your computer.
 2. Using the Webots IDE, open the `worlds/Arena.wbt` file.
 
 You may receive a warning about your computer's GPU not being good enough, which can be ignored.