[xcode] 清除 recent memu

打開 xcode，裡面常常出現許多已經沒有使用的 Project，下面的操作可以將 Project list 整個清空。

1. Launch Xcode
2. Select File->Open Recent->Clear Menu
3. Right-click the Xcode icon and select "Show All Windows". You should now see only your current document in the recents list at the bottom
4. Quit Xcode. The recents list should now only be populated with your single current project.