pg_auth_members, not pg_auth_member

Causes catalog tests to fail as we resort to oid, which does not exist.
Also causes exception in SUMMARY and terminates.

gpMgmt/bin/gpcheckcat

@@ -3873,7 +3873,7 @@ TableMainColumn['pg_amproc'] = ['amopclaid', 'pg_opclass']
 TableMainColumn['pg_appendonly'] = ['relid', 'pg_class']
 TableMainColumn['pg_attribute'] = ['attrelid', 'pg_class']
 TableMainColumn['pg_attribute_encoding'] = ['attrelid', 'pg_class']
-TableMainColumn['pg_auth_member'] = ['roleid', 'pg_authid']
+TableMainColumn['pg_auth_members'] = ['roleid', 'pg_authid']
 TableMainColumn['pg_autovacuum'] = ['vacrelid', 'pg_class']
 TableMainColumn['pg_depend'] = ['objid', 'pg_class']
 TableMainColumn['pg_exttable'] = ['reloid', 'pg_class']