Fix flash of accordion content during page load

[aduth]

🛠 Summary of changes

This updates Accordion component markup, removing invalid usa-accordion__container wrapper element, in order to allow the intended improvement from @18f/identity-design-system@9.1.0 to prevent flashing content during page load.

This follows a similar change from the introduction of that enhancement in 18F/identity-design-system#434 to alter the documented component markup, "[removing] an unnecessary and useless usa-accordion__container container element which is not standard to USWDS and would make the JavaScript hiding behavior ineffective".

📜 Testing Plan

1. Go to http://localhost:3000
2. Create an account
3. At password entry screen, refresh the page with cache disabled
4. Observe no flash of open accordion content for "Password safety tips"

👀 Screenshots

Screen recordings emulating slower page loads with "Fast 3G" preset in Chrome network simulation..

Before:

before.mov

After:

after.mov