Duplicated code in dist/bootstrap.css

Created by: Wendong-Wu

The following codes are repeated in both bootstrap.css and bootstrap.min.css. It looks like these codes are generated twice.

.container:before, .container:after { display: table; content: " "; }

.container:after { clear: both; }

.row:before, .row:after { display: table; content: " "; }

.row:after { clear: both; }