Remove visibility icon from projects list on dashboard and group page

## Why?

Because

* visibility level show on project page anyway
* it does not have much value. Main purpose of project list on dashboard is navigation. Avatar + project name helps this goal. Visibility icon have no effect here
* it makes UI worse because it brings separation between project avatar and name
* without visibility icon we have more space for project name. Especially important for laptops

## Screenshot

![Screenshot_2015-06-12_18.17.20](https://gitlab.com/gitlab-org/gitlab-ce/uploads/0e572388e9a337c5a535813911d08c89/Screenshot_2015-06-12_18.17.20.png)

P.S. Merge when 7-12-stable is created

See merge request !806