Fix parse errors in core-spec.pdf

Authored by RyanGlScott on Jul 16 2018, 8:51 AM.

Description

Fix parse errors in core-spec.pdf

Summary:
core-spec.pdf was emitting parse errors due to not specifying
role arguments in some uses of nth. This patch adds those
role arguments. (Credit goes to Richard Eisenberg for actually
figuring out what said arguments should be.)

Test Plan: Read it

Reviewers: goldfire, bgamari

Reviewed By: goldfire

Subscribers: rwbarton, thomie, carter

GHC Trac Issues: Trac #15373

Differential Revision: https://phabricator.haskell.org/D4965