Update linux_mint.sh

- get rid off output that is sent usually to stdout and stderr

mint/linux_mint.sh

@@ -114,7 +114,7 @@ echo "\
 e "Starte initiales Setup für Rechner mit frisch installiertem '${script_distro}' …"
 
 # Use APT proxy if available.
-ping -c 1 apt-proxy
+ping -c 1 apt-proxy > /dev/nul 2>&1
 if [ "$?" -eq "0" ]; then
 	e "Nutze APT-Proxy."
 	echo 'Acquire::https::Proxy "http://apt-proxy:3142";' > /etc/apt/apt.conf.d/01aptproxy