Document why closeOverKind is OK for determinism
Document why closeOverKind is OK for determinism

There's no point in converting the existing call sites to use
deterministic closeOverKinds if they never linearize the set.

Test Plan: it compiles, this is basically just documentation

Reviewers: simonpj, goldfire, simonmar, austin, bgamari

Reviewed By: bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2191

GHC Trac Issues: #4012

sdiehl/ghc,sdiehl/ghc,shlevy/ghc,olsner/ghc,shlevy/ghc,vikraman/ghc,shlevy/ghc,mettekou/ghc,vTurbine/ghc,ezyang/ghc,sdiehl/ghc,snoyberg/ghc,vikraman/ghc,snoyberg/ghc,mettekou/ghc,shlevy/ghc,vTurbine/ghc,olsner/ghc,ezyang/ghc,vTurbine/ghc,mettekou/ghc,olsner/ghc,olsner/ghc,sgillespie/ghc,snoyberg/ghc,vikraman/ghc,shlevy/ghc,olsner/ghc,mettekou/ghc,vikraman/ghc,sgillespie/ghc,vikraman/ghc,sgillespie/ghc,shlevy/ghc,mettekou/ghc,snoyberg/ghc,olsner/ghc,sgillespie/ghc,olsner/ghc,snoyberg/ghc,snoyberg/ghc,ezyang/ghc,sdiehl/ghc,vikraman/ghc,sdiehl/ghc,vikraman/ghc,mettekou/ghc,sgillespie/ghc,ezyang/ghc,ezyang/ghc,vTurbine/ghc,vTurbine/ghc,vTurbine/ghc,sgillespie/ghc,snoyberg/ghc,ezyang/ghc,vTurbine/ghc,ezyang/ghc,shlevy/ghc,mettekou/ghc,sdiehl/ghc,sgillespie/ghc,sdiehl/ghc