In general, fast-forward isn't an error -- it's usually a sign that things are going smoothly.
A "fast-forward" merge happens when you pull, but there aren't any locally committed changes to merge. Thus, your local repo can simply add any commits you just pulled from the remote (GitHub), and tack them onto the end of the local HEAD branch, and move HEAD to point to the latest commit. (Kind of like fast-forwarding to the end of a movie.)
However, in the case of Lab 4, we don't want things to go smoothly, because we are trying to create conflicts, so that we can learn how to resolve them.
Since your pull worked without giving you any error, it sounds like you may have missed the steps where you made changes to your local RestaurantMenu.java, and added/committed those changes. OR, you may have made your local changes, but maybe you pushed them up to GitHub BEFORE you edited the file on GitHub, so then when you pulled you just received the updates.
What I would recommend is that you try again to make some changes to both the local RestaurantMenu.java and the remote (GitHub) RestaurantMenu.java. Make sure you add/commit your local changes as well, and then try to pull. Hopefully you will see the CONLICTED file error message next time!