docs: Fix typo in PowerShell install script
When I documented the PS install script in I made a typo on the end.
@@ -82,7 +82,7 @@ bash -c "$(wget https://zmkfirmware.dev/setup.sh -O -)" '' --wget
<TabItem value="PowerShell">
```
-iex ((New-Object System.Net.WebClient).DownloadString('https://zmkfirmware.dev/setup.ps1'))"
+iex ((New-Object System.Net.WebClient).DownloadString('https://zmkfirmware.dev/setup.ps1'))
```
</TabItem>
