fix(chat): disableReactionsInChat feature flag not working

[Zaid0412]

Summary

This PR fixes the disableReactionsInChat feature by ensuring it is properly enforced in the chat UI. Additionally, it removes outdated or conflicting logic from a different file that was no longer functioning or necessary.

Changes

• Added a new check for disableReactionsInChat in the appropriate location.
• Removed old logic that was ineffective or duplicated.
• Ensured consistent behavior when the feature flag is toggled.

[jitsi-jenkins]

Hi, thanks for your contribution!
If you haven't already done so, could you please make sure you sign our CLA (https://jitsi.org/icla for individuals and https://jitsi.org/ccla for corporations)? We would unfortunately be unable to merge your patch unless we have that piece :(.