[FIX] website: fix images wall with link on image

After this commit, we prevent the slideshow from appearing when clicking
on an "Images Wall" snippet image that has been set as a link.

Steps to reproduce the bug:

- Drag and drop an "Images Wall" snippet onto the page.
- Add some images in the snippet.
- Click on an image within the snippet.
- In the editor text toolbar, click on the "Link" button.
- Set the URL of the link to "/contactus".
- Click on the "Save" button in the modal.
- Save the page.
- Click on the image with the link.
- Bug: The slideshow briefly appears before redirecting to the "contact
us" page.

task-3425624

closes odoo/odoo#128885

Signed-off-by: Colin Louis (loco) <loco@odoo.com>

addons/website/static/src/snippets/s_image_gallery/000.js

@@ -26,7 +26,7 @@ const GalleryWidget = publicWidget.Widget.extend({
      * @param {Event} ev
      */
     _onClickImg: function (ev) {
-        if (this.$modal) {
+        if (this.$modal || ev.currentTarget.matches("a > img")) {
             return;
         }
         var self = this;