Remove -Wamp flag (#11477)
Remove -Wamp flag (#11477)

Summary:
Add line
  "The deprecated ghc-flag -Wamp has been removed."
to the release notes for 8.8.1

Reviewers: bgamari, monoidal

Reviewed By: monoidal

Subscribers: rwbarton, carter

GHC Trac Issues: #11477

Differential Revision: https://phabricator.haskell.org/D5296

sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc