This message appears when you try to activate the free Tag Groups plugin and the Tag Groups Premium plugin at the same time. Since the free plugin is already included in the premium plugin, it will be automatically deactivated.
This is just an informational message and there is nothing you need to do.
So is it safe to remove the free plugin?
If you want to remove the free plugin entirely, you can do so without affecting the functionality of the premium plugin. Just make sure that you didn’t choose to delete your tag groups data in the Reset tab of the Tools settings. By default, you won’t delete this data.