Code review comment for lp://qastaging/~marcustomlinson/indicator-sound/fix-scroll-wheel-step-sizes

I haven't specified volume changes on the phone yet at all. <https://wiki.ubuntu.com/Sound#Volume_changes> But some quick testing shows me that Windows Phone has 30 steps from silent to maximum, iOS has 16, and Android has ... 8. Android notwithstanding, I'm leery about reducing the number of steps from 16.7 (?!) to 10 on Ubuntu.

I don't remember why I specced 5% (20 steps) for the -/+/arrow keys on the PC, and 10% for the mouse wheel. Perhaps it was because scrolling a scrollwheel repeatedly is harder than holding down a button. I don't have a mouse wheel here; how many clicks does a typical swipe cause?