Remove previewTimestamp code as it was required for hold-to-preview

Signed-off-by: Jakub Sztandera <kubuxu@protocol.ai>

javascript/imageViewer.js

@@ -1,12 +1,10 @@
 // A full size 'lightbox' preview modal shown when left clicking on gallery previews
-let previewTimestamp = Date.now();
 let previewDrag = false;
 let modalPreviewZone;
 
 function closeModal(force = false) {
   if (force) gradioApp().getElementById('lightboxModal').style.display = 'none';
   if (previewDrag) return;
-  if ((Date.now() - previewTimestamp) < 250) return;
   gradioApp().getElementById('lightboxModal').style.display = 'none';
 }
 
@@ -64,7 +62,6 @@ function showModal(event) {
   if (modalImage.style.display === 'none') lb.style.setProperty('background-image', `url(${source.src})`);
   lb.style.display = 'flex';
   lb.onkeydown = modalKeyHandler;
-  previewTimestamp = Date.now();
   event.stopPropagation();
 }