Fix preview ui button condition in the classic UI header

Author: koszti

core/trino-web-ui/src/main/resources/webapp/src/components/PageTitle.jsx

@@ -126,7 +126,7 @@ export class PageTitle extends React.Component<Props, State> {
                         </div>
                         <div id="navbar" className="navbar-collapse collapse">
                             <ul className="nav navbar-nav navbar-right">
-                                {info.previewEnabled && (
+                                {info.previewUiEnabled && (
                                     <li>
                                         <span className="navbar-cluster-info">
                                             <span className="text">