kali改回官方源后更新失败

官方源：

deb http://http.kali.org/kali kali-rolling main non-free contrib
deb-src http://http.kali.org/kali kali-rolling main non-free contrib

在文件 /etc/cat/sources.list中将官方源修改为：

deb http://http.kali.org/kali kali-rolling main contrib non-free non-free-firmware
deb-src http://http.kali.org/kali kali-rolling main contrib non-free non-free-firmware