Remove unnecessary clearfix from account page widgets

[aduth]

🛠 Summary of changes

Removes two instances of unnecessary clearfix, within the account page Security Key listing and Verified Information security disclosure text.

Historically, these were implemented using BassCSS grid, which uses float on individual columns. As documented, it's required to define clearfix on the column container when using BassCSS grid. In #4169, we migrated from BassCSS to USWDS for these grid layouts. The design system uses flexbox for grids and does not require a clearfix.

This is a continuation of the work in #9799 to eliminate the few remaining usages of clearfix.

📜 Testing Plan

Verify no visual regressions in display of Security Key and Verified Information widgets on account dashboard:

1. (Prerequisite: Have an account with security key and is identity-verified)
2. Go to http://localhost:3000
3. Sign in
4. Observe no collapsing content in "Security Key" listing or "Verified Information"