This is a nice mock-up for LibreOffice by Pauloop, a deviantart user. This Mock-up is unofficial and was made in Inkscape / Gimp.GTK2 Theme: Atolm by SkiesOfAzel and Native Icons: Faenza-Dark by Raul Vega.
This is a widget panel. To remove this text, login to your WordPress admin panel and go to Appearance >> Widgets, and drag & drop a widget into this widget panel. If you want to leave this area blank, simply put a blank Text widget into this widget panel which will overwrite this text.