icon should not be display in user#show page

[ff2248]

Before:

After:

Description

Accroding to redmine source code below:

• https://github.com/redmine/redmine/blob/986d487fcd18e6ba49e867e905559b575f003bd2/public/stylesheets/application.css#L1481-L1577

Icon's class name should be start with 'icon-` prefix.

[robspearman]

Thanks!