I installed rEFInd before realising it was not what I really needed. So I uninstalled it. However, despite uninstalling rEFInd, it still acts as my current bootloader when I power on my computer. I'm on the MacBook Air 11" Mid-2013 model. I figure there's a simple way for me to reverse this to get GRUB back, but this also does not follow the expected behaviour of uninstalling a package.