Fix accessibility issues due to aria-hidden and aria-labelledby in FileContent and CarouselFilmStrip

[corinagum]

Fixes #3810
Fixes #3811

Changelog Entry

• Fixes #3810. Removes aria-hidden from elements that have a focusable child, by @corinagum in PR #3836
• Fixes #3811. Removes erroneous aria-labelledby from carousel, by @corinagum in PR #3836

Description

This contains a few accessibility fixes when running FastPass on Web Chat.

Specific Changes

#3810 - Ensures aria-hidden elements do not contain focusable elements

• FileContent.js: Add aria-label alt text to download link, which was previously not being read.
• FileContent.js: Remove erroneous aria-hidden=true
• FileContent.js: Remove <ScreenReaderText />

#3811 - Ensure all ARIA attributes have valid values

• CarouselFilmStrip.js - remove erroneous aria-labelledby attribute
  • aria-labelledby is intended for visible text attributed as the label
  • When this is removed, no new a11y violations are detected
  • Remove (now)unused ariaID

• I have added tests and executed them locally
• I have updated CHANGELOG.md
• I have updated documentation

Review Checklist

This section is for contributors to review your work.

• Accessibility reviewed (tab order, content readability, alt text, color contrast)
• Browser and platform compatibilities reviewed
• CSS styles reviewed (minimal rules, no z-index)
• Documents reviewed (docs, samples, live demo)
• Internationalization reviewed (strings, unit formatting)
• package.json and package-lock.json reviewed
• Security reviewed (no data URIs, check for nonce leak)
• Tests reviewed (coverage, legitimacy)

[compulim]

Simpler code. :)