Description of the change

The code snippet in the over2 documentation doesn't compile

newtype Meter = Meter Int
derive newtype instance newtypeMeter :: Newtype Meter _
newtype SquareMeter = SquareMeter Int
derive newtype instance newtypeSquareMeter :: Newtype SquareMeter _

Checklist:

• Added the change to the changelog's "Unreleased" section with a reference to this PR (e.g. "- Made change (#0000)")
• Linked any existing issues or proposals that this pull request should close
• Updated or added relevant documentation
• Added a test for the contribution (if applicable)