fix typo in build.sh

Author: Sing-Li

build.sh

@@ -1,6 +1,6 @@
 #!/bin/bash
 cd /var/www/rocket.chat
-https://s3.amazonaws.com/rocketchatbuild/demo.rocket.chat-v.latest.tgz" -o rocket.chat.tgz
+curl -fSL "https://s3.amazonaws.com/rocketchatbuild/demo.rocket.chat-v.latest.tgz" -o rocket.chat.tgz
 tar zxvf rocket.chat.tgz  &&  rm rocket.chat.tgz
 cd /var/www/rocket.chat/bundle/programs/server
 npm install