Yes, this was fixed in a newer version of fourseven:scss but has been a recurring issue coming up in Issues.
If a package is in your versions file but not in your packages it means it’s a dependency of another package. So it’s probably necessary!
But remember, as with all platforms, upgrading your project involves both updating the tool (Meteor) itself and also packages which you use! It’s important to check the packages you’re using for information on what they’ve changed as the changes might be breaking or require other changes! (In this case fourseven warns that you should upgrade your version!)
Also, see important information at the bottom of this issue about another solution that would have worked for you, and ultimately the reason that fourseven:scss needed to be upgraded (essentially, the main issue was that node-sass needed to be recompiled).