Bug#47612 mtr - improving the report for valgrind erorrs

- Improve the report produced when a valgrind error is detected

mysql-test/include/mtr_warnings.sql

@@ -207,7 +207,7 @@ BEGIN
     WHERE suspicious=1;
 
   IF @num_warnings > 0 THEN
-    SELECT file_name, line
+    SELECT line
         FROM error_log WHERE suspicious=1;
     --SELECT * FROM test_suppressions;
     -- Return 2 -> check failed