Remove haskell-platform

The latest version haskell-platform features an entirely different
build system that does not play well with Homebrew, so it is being
removed in favor of the ghc and cabal-install formulae.

The binary installer can also be used instead:
  https://www.haskell.org/platform/mac.html

Closes #31609.
ruby-build 20140908

Closes #32168.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>