Remove String monkeypatch `to_range`
Remove String monkeypatch `to_range`

The functionality of this monkeypatch is now contained in
SolidusVolumePricing::RangeFromString.

solidusio-contrib/solidus_volume_pricing,solidusio-contrib/solidus_volume_pricing,solidusio-contrib/solidus_volume_pricing,solidusio-contrib/solidus_volume_pricing