Fix privileges on pg_statistic_ext.tableoid

The GRANT in system_views allowed SELECT privileges on various columns in
the pg_statistic_ext catalog, but tableoid was not included in the list.
That made pg_dump fail because it's accessing this column when building
the list of extended statistics to dump.

Discussion: https://postgr.es/m/8833.1560647898%40sss.pgh.pa.us

src/backend/catalog/system_views.sql

@@ -291,7 +291,7 @@ CREATE VIEW pg_stats_ext WITH (security_barrier) AS
     AND (c.relrowsecurity = false OR NOT row_security_active(c.oid));
 
 REVOKE ALL on pg_statistic_ext FROM public;
-GRANT SELECT (oid, stxrelid, stxname, stxnamespace, stxowner, stxkeys, stxkind)
+GRANT SELECT (tableoid, oid, stxrelid, stxname, stxnamespace, stxowner, stxkeys, stxkind)
     ON pg_statistic_ext TO public;
 
 CREATE VIEW pg_publication_tables AS