Using collapse on display:flex elements ie: row

Created by: iatek

I found this same problem in closed #20442 (closed), and I was wondering if it will be revisited for beta. Since row is display:flex, and collapse.show sets display:block, the displayed row is off.

<div class="container">
    <div class="row">
        <h4 class="col">
        <a href="#details" data-toggle="collapse">
            <span>Expand</span>
        </a>
      </h4>
    </div>
    <div id="details" class="row collapse" aria-expanded="false">
        <div class="col-6">
            <h3>Text</h3>
        </div>
        <div class="col-6">
            <h3>Text</h3>
        </div>
    </div>
    <div class="row" aria-expanded="true">
        <div class="col-6">
            <h3>Text</h3>
        </div>
        <div class="col-6">
            <h3>Text</h3>
        </div>
    </div>
</div>

http://codeply.com/go/UuAQvoRMiC