Removed some CSS rules as the toolbar can now be configured through the settings

As the toolbar can now be configured through the settings.json file, these custom CSS rules can be removed
It depends how much complexity we introduce by bringing in that fix (code wise or deployment wise). It feels like it's fairly important, as it's the only immediate way in which you can see that other people are in the document as well. However, I don't want to delay the Etherpad release too much.