Hi,
You can't do it like that. This will move all the scripts from the head at the end of the page, but this means that all the javascript which is inline on the page (and which expects the scripts from the head to be executed before) will be executed before the scripts from the head.
So if you want to do that, you need some code to automatically get the scripts inline on the page and move them to the end of the body, after the scripts from the head. It's possible but instead of just moving one line of code, you need to write a few dozen lines.
Rather than doing that, I would recommend using JCH Optimize:
extensions.joomla.org/extension/jch-optimize/
It can improve the JS loading in a much better way than this and optimize many other things too.