apt-key deprecation of legacy trusted.gpg

When running the installer and wanting rspamd, you'll get this error on Ubuntu 22.04: W: http://rspamd.com/apt-stable/dists/jammy/InRelease: Key is stored in legacy trusted.gpg keyring (/etc/apt/trusted.gpg), see the DEPRECATION section in apt-key(8) for details.

We shall update the commands to add the rspamd repo. They differ from the current guide on the rspamd website:

sudo apt-get install -y lsb-release wget # optional
CODENAME=`lsb_release -c -s`
sudo mkdir -p /etc/apt/keyrings
wget -O- https://rspamd.com/apt-stable/gpg.key | gpg --dearmor | sudo tee /etc/apt/keyrings/rspamd.gpg > /dev/null
echo "deb [arch=amd64 signed-by=/etc/apt/keyrings/rspamd.gpg] http://rspamd.com/apt-stable/ $CODENAME main" | sudo tee /etc/apt/sources.list.d/rspamd.list
echo "deb-src [arch=amd64 signed-by=/etc/apt/keyrings/rspamd.gpg] http://rspamd.com/apt-stable/ $CODENAME main"  | sudo tee -a /etc/apt/sources.list.d/rspamd.list
sudo apt-get update
sudo apt-get --no-install-recommends install rspamd