Update phpBB/language/en/posting.php

[ticket/11220] Improvement of info-popup of "[list=]"-Button

A Improvement of the info-popup of the bbcode-button "[list=]" at the posting-editor, which appear if the user moves with his mouse over the button. The new explaination gives a more detailed information of the usage the user, so he can easier understand the usage of this bbcode.

PHPBB3-11220