Mixcloud Shortcode: Autoplay Does Not Work

#### Steps to reproduce the issue

Embed any track from Mixcloud as per [Mixcloud Audio Player Support Page](https://en.support.wordpress.com/mixcloud-audio-player/) with `autoplay=1`. Example:

`[mixcloud https://www.mixcloud.com/theversion/the-version-radio-episode-3/ width=100% height=180 autoplay=1]`

#### What I expected
The track should autoplay

#### What happened instead
The track does not autoplay

**Source**

#user-report 2922663-zen

Reproduce the Mixcloud shortcode using the linked support guidance and the provided autoplay=1 example. Trace the shortcode entry point and verify how the embed is rendered; the issue is done when an embedded track autoplays as expected.

Written by the indexing model from the issue text.