[Generate.sh] Fixed broken pipe error message

generate_config.sh

@@ -205,8 +205,8 @@ DBUSER=mailcow
 
 # Please use long, random alphanumeric strings (A-Za-z0-9)
 
-DBPASS=$(LC_ALL=C </dev/urandom tr -dc A-Za-z0-9 | head -c 28)
-DBROOT=$(LC_ALL=C </dev/urandom tr -dc A-Za-z0-9 | head -c 28)
+DBPASS=$(LC_ALL=C </dev/urandom tr -dc A-Za-z0-9 2> /dev/null | head -c 28)
+DBROOT=$(LC_ALL=C </dev/urandom tr -dc A-Za-z0-9 2> /dev/null | head -c 28)
 
 # ------------------------------
 # HTTP/S Bindings