[Privacy Panel] merge request to apps

Instead of having those 2 tests accessing internal method/properties you should extract the mock privacy-panel app in a variable and just have one test doing `this.element.click` and asserting that `launch` was called on the mock app. It will cover the same code but will be easier to maintain (we don't care if `_ppApp` gets renamed for example, this shouldn't require us to update the test)