Description

This PR updates the header component text styling to use semantic HTML and consistent heading styles. The changes include:

• Changed text element from <p> to <h2>
• Updated text variant from bodyMdBold to headingSm
• Improves accessibility by using proper heading hierarchy
• Maintains consistent styling across multiple pages using the header component

Related issues

Partially fixes: #29306

Manual testing steps

1. Navigate to pages using the header component (NFT details, Connections, Permissions pages)
2. Verify header text appears correctly with new heading styles
3. Verify layout and alignment remain consistent
4. Check that accessibility tools properly recognize the heading structure

Screenshots/Recordings

Before

After

Pre-merge author checklist

• I've followed MetaMask Contributor Docs and MetaMask Extension Coding Standards.
• I've completed the PR template to the best of my ability
• I've included tests if applicable
• I've documented my code using JSDoc format if applicable
• I've applied the right labels on the PR (see labeling guidelines). Not required for external contributors.

Pre-merge reviewer checklist

• I've manually tested the PR (e.g. pull and build branch, run the app, test code being changed).
• I confirm that this PR addresses all acceptance criteria described in the ticket it closes and includes the necessary testing evidence such as recordings and or screenshots.