PhET-iO id for hiding temperature radio buttons incorrect in examples.md

[Nancy-Salpepi]

For https://github.com/phetsims/qa/issues/970

In the examples doc under Control Temperature Units >> Layer Model Screen the PhET-iO id to hide the temperature radio buttons is listed as: greenhouseEffect.layerModelScreen.view.temperatureUnitsControl.temperatureUnitsRadioButtonGroup.visibleProperty but in the studio tree, the buttons are hidden using: greenhouseEffect.layerModelScreen.view.temperatureUnitsControl.visibleProperty

[arouinfar]

Good catch @Nancy-Salpepi! I fixed it in the above commit, closing.

This is another example where https://github.com/phetsims/phet-io-sim-specific/issues/21 would be helpful.