v4 - Some grid docs examples still use defunct .visible-xs-block

Created by: monoblaine

According to the migration guide, the visible-*-block classes are gone:

The old classes (.hidden-xs .hidden-sm .hidden-md .hidden-lg .visible-xs-block .visible-xs-inline .visible-xs-inline-block .visible-sm-block .visible-sm-inline .visible-sm-inline-block .visible-md-block .visible-md-inline .visible-md-inline-block .visible-lg-block .visible-lg-inline .visible-lg-inline-block) are gone.

However, the grid example here still uses this technique:

<div class="clearfix visible-xs-block"></div>

Am I missing something?