[FIX] website_forum: fix selector in event of the submit btn of a post

A comma was removed in the following commit for no reason
912996fe90 . Because of this, the click
event of the forum post submit button was not working.

task-2312878
Part of #66316

X-original-commit: 3509d438133de46ef02bb70255c7cd737a695f15

addons/website_forum/static/src/js/website_forum.js

@@ -151,7 +151,7 @@ publicWidget.registry.websiteForum = publicWidget.Widget.extend({
             wysiwygLoader.load(self, $textarea[0], options).then(wysiwyg => {
                 // float-left class messes up the post layout OPW 769721
                 $form.find('.note-editable').find('img.float-left').removeClass('float-left');
-                $form.on('click', 'button .a-submit', () => {
+                $form.on('click', 'button, .a-submit', () => {
                     wysiwyg.save();
                 });
             });