user-guide: Mention COMPLETE pragma in release notes
user-guide: Mention COMPLETE pragma in release notes

Reviewers: austin

Subscribers: rwbarton, thomie

GHC Trac Issues: #14305

Differential Revision: https://phabricator.haskell.org/D4059

sdiehl/ghc,ezyang/ghc,shlevy/ghc,ezyang/ghc,ezyang/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,shlevy/ghc,ezyang/ghc,shlevy/ghc,shlevy/ghc,shlevy/ghc,shlevy/ghc,sdiehl/ghc,ezyang/ghc,ezyang/ghc,sdiehl/ghc,shlevy/ghc,ezyang/ghc,sdiehl/ghc