Move the "additional restrictions" comment to ALTER TABLE ADD
CONSTRAINT instead of ADD CONSTRAINT USING INDEX; and in the latter
instead indicate that partitioned tables are unsupported

Noted by David G. Johnston
Discussion: https://postgr.es/m/CAKFQuwY4Ld7ecxL_KAmaxwt0FUu5VcPPN2L4dh+3BeYbrdBa5g@mail.gmail.com