message: Fix small docs typo
diff: @@ -25,7 +25,7 @@ export PATH="$PATH:/opt/etcher-cli"
  - On Windows 10 and Windows 8
  - Open *Control Panel*
  - - Open *System
  + - Open *System*
  - Click the *Advanced system settings* link
  - Click *Environment Variables*
  - Find the `PATH` environment variable, and click *Edit*
  