Fixed broken documentation

I was trying to setup my FML workspace to try and help update Forge, however when trying to setup FML, I ran into some broken documentation.

It says it needs the command "gradle setupDevWorkspace", however when I did, it gave me an error saying that it found no commands by that name in the project "fml".

So in the end, I found out that the correct command was "gradle setupFML" through the command that lists all available commands in the project.

If I'm being stupid, or I'm doing something wrong, please say. And, feel-free to deny this request if you feel it's incorrect.