doc: Add additional SQL features codes from SQL:2023
These were mysteriously omitted in c9f57541d9.
Branch------master
Details-------https://git.postgresql.org/pg/commitdiff/1c77de98017022e45a0b12ddb71e202d55551f68
Modified Files--------------src/backend/catalog/sql_features.txt | 2 ++1 file changed, 2 insertions(+)
