Summary:
The list was 14 years old, and there don't seem to be any problems
with seq# or par#; the other par*# primops were not actually
implemented at all and were removed in D758.

Test Plan:
validate; will also try to locally validate an unregisterised build
in case there was some truth to the deleted comment

Reviewers: austin

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D759

GHC Trac Issues: #10191