Change Authorizations header to h3 (use UnderlinedHeaderAuth)

[Yayabtw]

What/Why/How?

Change the "Authorizations:" header from an h5 to an h3 to restore correct heading hierarchy inside operation details.

Why:

• Operation title uses h2, Authorizations: was h5 and other sections used h3 which breaks semantic heading order.
• Fixes accessibility and document outline for screen readers and improves SEO.

What changed:

• Render Authorizations: with an h3-styled header (UnderlinedHeaderAuth) instead of an h5.
• Ensure visual styles (underlined, uppercase) remain identical to prior appearance.

How:

• Replace AuthHeader to use UnderlinedHeaderAuth in:
  • src/components/SecurityRequirement/styled.elements.ts
• UnderlinedHeaderAuth is defined in src/common-elements/headers.ts as an h3-based styled component.

Reference

• Fixes / references issue: Inaccurate heading hierarchy #2741

Tests

Screenshots (optional)

Check yourself

• Code is linted
• Tested
• All new/updated code is covered with tests