Simple layout: Method of clearfix diffrent from 7.x-4.3

In this release, there was a minor change to the clearing of the header, main, and footer of simple.layout.css that have broken the clearing.

7.x-4.3 (works)

.l-header:after,
.l-main:after,
.l-footer:after {
  content: "";
  display: table;
  clear: both;
}

7.x-4.4 (does not work)

.l-header:after,
.l-main:after,
.l-footer:after {
  content: " ";
  display: block;
  clear: both;
}