Update 8.0.2 release notes for Trac #12784
The fix for Trac #12220 exposed some ill-typed programs which passed the typechecker
in GHC 8.0.1 but now fail to typecheck in GHC 8.0.2. It's a bit difficult to
characterize what exactly triggers this bug, but we at least have a minimal
example and a simple fix to illustrate the problem and solution, so let's
add that the the 8.0.2 release notes to advertise this change.
Resolves Trac #12784.
Reviewers: rwbarton, austin, bgamari
Reviewed By: bgamari
Differential Revision: https://phabricator.haskell.org/D2682
GHC Trac Issues: Trac #12784