The very base class is the wrong place for it because
`FreeModSelectOverlay` inherits from it, and that one has different
assumptions and rules than "user" selection. In particular, in non-user
selection, more than one rate adjust mod may be active, which breaks the
mod speed hotkey's basic assumptions.
Being able to flip doesn't really feel all that good and `master` was
already clamping, so let's just bring that back for now. Flipping can be
reconsidered in a follow-up if it actually can be made to behave well.