This section of text is from the Define Pages Editor located under Tools in the Admin.
You can use either the language-file in /includes/languages/english/MYTEMPLATE/about_us.php or this file separately for this page or, you can use both together.
To remove the language file definition, do not delete the define statement, set it to be blank. Example: define('TEXT_INFORMATION', '');
To remove this section of the text (which you're reading right now), delete it from the Define Pages Editor, located under Tools in the Admin.