Note that `ghost IS NOT TRUE` is equivalent to `ghost = 'f' OR ghost is
null`:

(true), (false), (NULL)) AS t (flag);
 flag | ?column? | ?column?
------+----------+----------
 t    | f        | f
 f    | t        | t
      | t        | t
(3 rows)

This makes it a little easier to create partial indexes for this (as only
one condition is needed).

Closes #43304.