sql: incorrect types for some pg_constraint columns

[arulajmani]

Describe the problem

As per the pg_constraint schema here: https://www.postgresql.org/docs/current/catalog-pg-constraint.html, a few of the columns seem to have an incorrect data type. For example, columns such as confdeltype and confuptypeand are represented as strings in CRDB, but are single char columns in Postgres. We should match our schema to Postgres.

[rafiss]

Let's go through all the diffs in pg_catalog_test_expected_diffs.json and fix the columns that have a diff like this:

{
      "oid": 25,
      "dataType": "text",
      "expectedOid": 18,
      "expectedDataType": "char"
}

there's only 8 of them, so we can do the change manually. @mnovelodou could you get to this when you have a chance?