[skip ci] Fix bug71162.phpt xfail message (GH-15506)

The test failure is unlikely to be caused by `SessionHandlerInterface`
not being available.

Author: cmb69

ext/session/tests/user_session_module/bug71162.phpt

@@ -5,7 +5,7 @@ session
 --INI--
 session.use_strict_mode=0
 --XFAIL--
-Current session module is designed to write empty session always. In addition, current session module only supports SessionHandlerInterface only from PHP 7.0.
+Current session module is designed to write empty session always.
 --FILE--
 <?php
 class MySessionHandler extends SessionHandler implements SessionUpdateTimestampHandlerInterface