Feedback Form should pass when disclaimer isn't present

[lexi-taylor]

Description

Feedback Form had a hard requirement for disclaimer to be present, this was by mistake, the disclaimer should be an optional (not included) property

• Valibot supports a exactOptional validator but it's in a version webchat doesn't have yet.

• This allows the disclaimer to operate similarily to exactOptional

• 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]

Please also update CHANGELOG.md. As this change is small, you can just add the PR number to the existing entry.