Update .cabal files for Cabal 2.1

cabal introduces SPDX identifier, and as such we need to change the
BSD3 license name. Also the >= qualifier is no longer prefered.

Test Plan: ./validate

Reviewers: bgamari, erikd, simonmar

Reviewed By: bgamari

Subscribers: alpmestan, rwbarton, thomie, carter

Differential Revision: https://phabricator.haskell.org/D4406