There is no safe way to partially upgrade your system.
You could add all the gnome related packages to ignorepkg in /etc/pacman.conf but that is not something I would recommend. That is a good way to break your system.
That being said, are you sure that is the issue here? That looks like a package conflict. Are you sure it is due to it not being updated? What is trying to pull mutter in? Is something explicitly look for mutter >= 43?