Fix device discovery under GStreamer 1.16

src/CallManager.h

@@ -53,6 +53,7 @@ public:
 public slots:
         void sendInvite(const QString &roomid, bool isVideo);
         void syncEvent(const mtx::events::collections::TimelineEvents &event);
+        void refreshDevices() { session_.refreshDevices(); }
         void toggleMicMute();
         void toggleCameraView() { session_.toggleCameraView(); }
         void acceptInvite();

src/WebRTCSession.cpp

@@ -1292,6 +1292,7 @@ WebRTCSession::refreshDevices()
                         addDevice(GST_DEVICE_CAST(l->data));
                 g_list_free(devices);
         }
+        emit devicesChanged();
 #endif
 }