Avoided a problem with the on-screen keyboard being re-created after shutdown on Windows

modules/juce_gui_basics/native/juce_win32_Windowing.cpp

@@ -802,7 +802,7 @@ struct OnScreenKeyboard   : public DeletedAtShutdown,
         startTimer (10);
     }
 
-    JUCE_DECLARE_SINGLETON_SINGLETHREADED (OnScreenKeyboard, true)
+    JUCE_DECLARE_SINGLETON_SINGLETHREADED (OnScreenKeyboard, false)
 
 private:
     OnScreenKeyboard()