The 0.01 `Precision` spec on `DifficultyMultiplierDisplay.Current` would
cause the difficulty multiplier to use a different midpoint rounding
strategy than `double.ToString()`, which is the one that the song select
footer relies on. For example, a value of 0.015 would be rounded down
to 0.01 by `double.ToString()`, but rounded up to 0.02
by `BindableDouble`.
Fix the discrepancy by just deleting the `Precision` spec. Since the
value of the bindable would go through `ToLocalisableString(@"N2")`
anyway, it was redundant as is.
Fixes#19889.
