[amp-auto-ads] ad resize is failing

## What's the issue?

`amp-auto-ads` is not able to resize ads and it's breaking the page when it happens

## How do we reproduce the issue?

The error happens most of the time, but not always. In my tests I found out that the `i-amphtml-layout-awaiting-size` class is breaking the ads because of it's CSS.

URL: https://sample.denakop.com/featured/top-fashion-trends-to-look-for-in-every-important-collection/?amp
amp-auto-ads config object: http://jsoneditoronline.org/#left=cloud.a2b84922eb2745f48bc2683afc15ede1
Screenshot: https://imgur.com/a/clN7JYB

## What browsers are affected?

All browsers and devices

## Which AMP version is affected?

Version: 2011070101001 (current version)