[FIX] web_editor: always apply checklist class on convert p to checklist

When converting a paragraph to a checklist, we first apply the checklist
class and then take the paragraph's attributes and apply it to the new
list. If said attributes included the "class" attribute, it wrote over
the checklist class.

Part-of: odoo/odoo#92200

addons/web_editor/static/src/js/editor/odoo-editor/src/commands/toggleList.js

@@ -40,9 +40,13 @@ HTMLElement.prototype.oToggleList = function (offset, mode = 'UL') {
 HTMLParagraphElement.prototype.oToggleList = function (offset, mode = 'UL') {
     const restoreCursor = preserveCursor(this.ownerDocument);
     const list = insertListAfter(this, mode, [[...this.childNodes]]);
+    const classList = [...list.classList];
     for (const attribute of this.attributes) {
         list.setAttribute(attribute.name, attribute.value);
     }
+    for (const className of classList) {
+        list.classList.toggle(className, true); // restore list classes
+    }
     this.remove();
 
     restoreCursor(new Map([[this, list.firstChild]]));