Removed a translation for a symbol in the admin header.

I've tried several text but none really made a difference between admin
menu and going back to the blog.Since I use entypo font within the admin
panel, I thought that maybe one icon could give a nice feeling.

The goal is that the first button is a goto blog public's home link. So
I arbitrarly chose an open book icon. Let's see how it fares and adapt.