[MM-55333] Convert ./components/post_view/floating_timestamp/floating_timestamp.tsx from Class Component to Function Component (#25401)

Co-authored-by: Mattermost Build <build@mattermost.com>

webapp/channels/src/components/post_view/floating_timestamp/floating_timestamp.tsx

@@ -17,10 +17,7 @@ type Props = {
     isRhsPost?: boolean;
 }
 
-export default class FloatingTimestamp extends React.PureComponent<Props> {
-    render() {
-        const {createAt, isScrolling, isRhsPost, toastPresent} = this.props;
-
+const FloatingTimestamp = ({createAt, isScrolling, isRhsPost, toastPresent}: Props) => {
     if (createAt === 0) {
         return null;
     }
@@ -47,5 +44,6 @@ export default class FloatingTimestamp extends React.PureComponent<Props> {
             </div>
         </div>
     );
-    }
-}
+};
+
+export default React.memo(FloatingTimestamp);