Update pgx tests

Author: kyleconroy

internal/endtoend/testdata/cast_null/pgx/go/query.sql.go

@@ -1,5 +1,9 @@
 CREATE TABLE foo (bar text);
 
--- name: CastCoalesce :many
-SELECT coalesce(bar, '')::text as login
+-- name: ListNullable :many
+SELECT
+  NULL::text as a,
+  NULL::integer as b,
+  NULL::bigint as c,
+  NULL::time as d
 FROM foo;