Thinko in commit a4523c5a.  It doesn't really affect anything at
present, but it would be a problem if any tests added later in this
file ought to get index-only-scan plans.  Back-patch, like the previous
commit, just to avoid surprises in case we add such a test and then
back-patch it.

Nikita Glukhov

Discussion: https://postgr.es/m/8b70135d-ad38-bdd8-ac92-71e2b3c273cf@postgrespro.ru