SQL/JSON: Fix some obsolete comments.
JSON_OBJECT(), JSON_OBJETAGG(), JSON_ARRAY(), and JSON_ARRAYAGG()
added in
7081ac46ace are not transformed into direct calls to
user-defined functions as the comments claim. Fix by mentioning
instead that they are transformed into JsonConstructorExpr nodes,
which may call them, for example, for the *AGG() functions.
Reported-by: Alexander Lakhin <exclusion@gmail.com>
Discussion: https://postgr.es/m/
058c856a-e090-ac42-ff00-
ffe394f52a87%40gmail.com
Backpatch-through: 16