Backport Bug #45827 Stmt using two autoinc values does not produce unsafe warning

One statement that have more than one different tables to update with 
autoinc columns just was marked as unsafe in mixed mode, so the unsafe 
warning can't be produced in statement mode.
      
To fix the problem, mark the statement as unsafe in statement mode too.

mysql-test/suite/rpl/t/rpl_variables_stm.test

@@ -471,7 +471,9 @@ BEGIN
 END|
 DELIMITER ;|
 
+--disable_warnings
 INSERT INTO trigger_table VALUES ('bye.');
+--enable_warnings
 
 
 --echo ==== Insert variables from a prepared statement ====