campaigns: hide YouTube from Percy

Created by: LawnGnome

Fixes #12170 (closed).

This PR also unifies the one other test where we hide an element from Percy into the same CSS class, since we need to declare it in two places to be usable with Storybook and non-Storybook tests.

I have a support ticket open with Percy/BrowserStack right now to fix my account, but until that happens, I would appreciate someone hitting "approve" in Percy.