Don't display the output of wget

wiki/src/install/inc/steps/install_tails_installer.inline.mdwn

@@ -30,7 +30,7 @@ Installer</span>.</p>
 1. If you are running Debian, execute the following command to add the
    Tails APT repository to your system:
 
-       wget -O - https://labs.riseup.net/code/attachments/download/1052/tails-apt.key | sudo apt-key add -
+       wget -q -O - https://labs.riseup.net/code/attachments/download/1052/tails-apt.key | sudo apt-key add -
        echo "deb http://deb.tails.boum.org/ feature-jessie main" | \
             sudo tee /etc/apt/sources.list.d/tails.list