[FIX] web_editor: allow to delete backward a contenteditable

Deleting a node content-editable false did not work.

X-original-commit: odoo/odoo@de42d0f965
Part-of: odoo/odoo#77377

addons/web_editor/static/lib/odoo-editor/src/commands/deleteBackward.js

@@ -75,6 +75,10 @@ HTMLElement.prototype.oDeleteBackward = function (offset, alreadyMoved = false)
             leftNode.remove();
             return;
         }
+        if (leftNode.getAttribute && leftNode.getAttribute('contenteditable') === 'false') {
+            leftNode.remove();
+            return;
+        }
         if (!isBlock(leftNode) || isVisibleEmpty(leftNode)) {
             /**
              * Backspace just after an inline node, convert to backspace at the