Undo allowing type abstractions via` ScopedTypeVariables`
Summary
What was proposed in https://github.com/ghc-proposals/ghc-proposals/pull/604/
The important thing to do is get this in 9.8.
Steps to reproduce
TODO, I am not totally sure which parts of TypeAbstractions
are currently implemented.
Expected behavior
See proposal --- we want deprecation warnings that do not exist today