CoreAudio: No longer consider a device stopping to be a failure

The device may need to stop because it is about to restart with new
settings.

e.g. When the DemoRunner is started while the microphone is set to
44.1KHz and the speakers are set to 48KHz in Audio MIDI Settings, one of
the devices must be restarted in order for the AudioDeviceCombiner to
work. In this situation, stopping one device shouldn't count as an
error, because the device will be started again with new, compatible,
settings.

modules/juce_audio_devices/native/juce_CoreAudio_mac.cpp

@@ -2065,7 +2065,8 @@ private:
             if (target != nullptr)
                 target->audioDeviceStopped();
 
-            error = true;
+            // The audio device may stop because it's about to be restarted with new settings.
+            // Stopping the device doesn't necessarily count as an error.
         }
 
         void audioDeviceError (const String& errorMessage) override