Can't set fn as sprint key on controls

Put the summary of the bug you're having here

What I expected to happen was...:
To use the sprint key as fn (Function) because I like the last button from right to left that on mac is fn

What actually happened was...:
It doesn't work, I tried to use fn (function) as keybind of Sprint just as 1.12.2 at older

Steps to Reproduce:
1. Just enable the sprint key to be set as function just as 12.2