Bug 1094878 - Call is not on hold anymore after hanging up another call even though the icon says it is

Sorry, I can't comment on the line where this should go using the GitHub UI. In ```calls_handler.js:L871```, we should add the following:
```js
CallScreen.setShowOnHold(
  !telephony.active &&
  telephony.calls.some((call) => call.state === 'held');
```