message: Fix macOS webdriver update command name
diff: @@ -211,7 +211,7 @@ yarn run webdriver-update --versions.chrome=77.0.3865.120
  Or if you are using macOS (OS X), run:
  ```
  # automatically select the correct Chrome version
  -yarn run webdriver-update-webdriver-update-macos
  +yarn run webdriver-update-macos
  ```
  