Fixed typo (widow) (#3215)

Author: hubalazs

xml/System.Windows/SystemCommands.xml

@@ -197,7 +197,7 @@
       </Parameters>
       <Docs>
         <param name="window">The window to restore.</param>
-        <summary>Restores the specified widow.</summary>
+        <summary>Restores the specified window.</summary>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>