a nit: the notes for ghc are duplicated/redundant following a port upgrade process

[Kenneth Wolcott]

    Note: variant `ghc +prebuilt` is used as a fallback when `ghc`
    cannot be compiled, whereas port `ghc-prebuilt` is necessary to bootstrap
    Haskell build tools, including port `ghc`.
  ghc-prebuilt has the following notes:
    Note: port `ghc-prebuilt` is necessary to bootstrap Haskell
    build tools, including port `ghc`, whereas port variant `ghc +prebuilt`
    is used as a fallback when `ghc` cannot be compiled.

Just an observation...

Thanks,
Ken Wolcott