winrt: Remove superfluous socketDescriptor assignment

Change-Id: I567418f21eef2f07e0d5283f46a02305d1153e0a
Reviewed-by: Samuel Nevala <samuel.nevala@intopalo.com>
Reviewed-by: Maurice Kalinowski <maurice.kalinowski@theqtcompany.com>

src/network/socket/qnativesocketengine_winrt.cpp

@@ -499,7 +499,6 @@ void QNativeSocketEngine::close()
         if (socket) {
             hr = socket->Close();
             Q_ASSERT_SUCCEEDED(hr);
-            d->socketDescriptor = -1;
         }
         d->socketDescriptor = -1;
     }