release.sh: fix Debian source repository configuration
release.sh: fix Debian source repository configuration

Debian switched to deb822 sources.list:

https://twitter.com/zekjur/status/1572622368492888065

i3/i3,i3/i3,i3/i3,Airblader/i3,Airblader/i3,Airblader/i3,stapelberg/i3,stapelberg/i3,stapelberg/i3,Airblader/i3,stapelberg/i3,i3/i3