Fix: remove unused single letter class in carousel

[OEvgeny]

Fixes #5323

Changelog Entry

• Fixes #5323. Removed unused CSS class from carousel component, eliminating unintended styling, in PR #5325, by @OEvgeny

Description

This PR removes an unused single-letter CSS class c from the CarouselFilmStrip component.

Design

When evanw/esbuild#3484 is resolved by esbuild, we'll update our build configuration to make it harder to target our minified classes.

Specific Changes

• Removed the class c from the div with class webchat__carousel-filmstrip__complimentary-content in CarouselFilmStrip.js

• 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)