Remove unitless line height

[jacobp100]

Since we're doing a major release anyway, I want to remove this, as it does the wrong thing in the following case,

const Component = styled(View)`
  font: 16px/1.5 system;
`

const IncorrectLineHeight = () => (
  <Component style={{ fontSize: 24 }} />
)

[kristerkari]

Looks good :)