[polaris.shopify.com] HomepagePromos with video should have a fallback for reduced motion

[aveline]

Issue summary

Home page renders as above on Mac OS when reduce motion is enabled.

Expected behavior

A static image should render as a fallback when reduce motion is enabled, instead of the video in the current Polaris for VS Code promo box.

Actual behavior

See screenshot above

Steps to reproduce the problem

1. Enable reduce motion in System Preferences
2. Navigate to polaris.shopify.com in Chrome, Safari, or Firefox