[FIX] web_editor: update image gallery miniatures

When changing an image in the image gallery snippet, the miniature was not
updated. It was due to the 'save' event that was not triggered.

task-2438556

closes odoo/odoo#65461

Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>

addons/web_editor/static/src/js/wysiwyg/widgets/media.js

@@ -497,6 +497,7 @@ var FileWidget = SearchableMediaWidget.extend({
                     self.$media.removeAttr('data-' + attr);
                 });
             }
+            self.$media.trigger('save')
             return self.media;
         });
     },