Update install instruction for Debian 12+

README.md

@@ -65,11 +65,8 @@ or download .deb packages from [here](https://launchpad.net/~papirus/+archive/ub
 Debian users also can install Papirus from our [PPA](https://launchpad.net/~papirus/+archive/ubuntu/papirus), but the commands will differ:
 
 ```
-sudo sh -c "echo 'deb http://ppa.launchpad.net/papirus/papirus/ubuntu focal main' > /etc/apt/sources.list.d/papirus-ppa.list"
-
-sudo apt-get install dirmngr
-sudo gpg --no-default-keyring --keyring gnupg-ring:/etc/apt/trusted.gpg.d/papirus.gpg --keyserver keyserver.ubuntu.com --recv E58A9D36647CAE7F
-sudo chmod 644 /etc/apt/trusted.gpg.d/papirus.gpg
+sudo sh -c "echo 'deb http://ppa.launchpad.net/papirus/papirus/ubuntu jammy main' > /etc/apt/sources.list.d/papirus-ppa.list"
+sudo wget -qO /etc/apt/trusted.gpg.d/papirus-ppa.asc 'https://keyserver.ubuntu.com/pks/lookup?op=get&search=0x9461999446FAF0DF770BFC9AE58A9D36647CAE7F'
 sudo apt-get update
 sudo apt-get install papirus-icon-theme
 ```