Don't trigger decoration repaint when ShellClient geometry changes

The geometry change will trigger an update through the signals on the
decoration anyway. Thus a dedicated repaint is not needed.

shell_client.cpp

@@ -492,7 +492,6 @@ void ShellClient::doSetGeometry(const QRect &rect)
             m_internalWindow->setGeometry(windowRect);
         }
     }
-    triggerDecorationRepaint();
     if (hasStrut()) {
         workspace()->updateClientArea();
     }