Fix test

Author: nikic

ext/mbstring/tests/mb_substitute_character.phpt

@@ -25,7 +25,7 @@ var_dump(bin2hex(mb_convert_encoding("\xe2\x99\xa0\xe3\x81\x82", "CP932", "UTF-8
 
 var_dump(mb_substitute_character('BAD_NAME'));
 ?>
---EXPECT--
+--EXPECTF--
 bool(true)
 int(12356)
 string(8) "82a282a0"
@@ -38,5 +38,6 @@ string(4) "82a0"
 bool(true)
 string(6) "entity"
 string(20) "262378323636303b82a0"
-ERR: Warning
+
+Warning: mb_substitute_character(): Unknown character in %s on line %d
 bool(false)