Fix styling of .brand in topbar

Created by: nikku

Somehow the styling of .brand in topbar is incorrect. The sample on the documentation page implies the usage of .brand on an anchor field:

<a class="brand" href="#">Bootstrap</a>

This however, breaks with the :hover styling for brand defined in patterns.less

.topbar {
  ...

  // Hover and active states
  .brand a:hover,
  ul .active > a {
     ...
  }

.brand a:hover should probably be changed to .brand:hover (which fixes the issue).