Reflect property change when unpairing

There's no pairStatusChanged when the device is not connected to
anything (be it because it's unreachable at the moment).

core/device.cpp

@@ -176,6 +176,7 @@ void Device::unpair()
         dl->userRequestsUnpair();
     }
     KdeConnectConfig::instance()->removeTrustedDevice(id());
+    Q_EMIT trustedChanged(false);
 }
 
 void Device::pairStatusChanged(DeviceLink::PairStatus status)

kcm/kcm.cpp

@@ -271,6 +271,7 @@ void KdeConnectKcm::unpair()
         return;
     }
 
+    setCurrentDeviceTrusted(NotTrusted);
     currentDevice->unpair();
 }