pgsql: Fix information schema for catalogued not-null constraints

Fix information schema for catalogued not-null constraints

The column check_constraints.check_clause should be like

    col IS NOT NULL

without a surrounding CHECK (...).

Discussion: https://www.postgresql.org/message-id/09489196-0bc1-e796-c43e-63425f7c5910@eisentraut.org

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/a0a5e0feb35c1209e340046dc4e40af3b0e79d59

Modified Files
--------------
src/backend/catalog/information_schema.sql | 2 +-
src/include/catalog/catversion.h           | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)