[0.17.18] Custom gui scale

[dutchgameer2004]

I normally play with a custom gui scale of 95% because numbers look weird on 100% and 75% is to small but in 0.17.17 the custom gui option got changed so you could only do it in steps of 25%. I didn't see it in the changelog so i presume this is a unintentional bug.

[kovarex]

It is the other way around, it was unintentional bug that it was possible to be not a multiplication of 25%.

We have a good reasons to only allow multiplications of 25%.