fix(docs): remove lock/unlock buttons from interactive demo

Lock mode buttons depend on PR #1939 which isn't published yet.
Remove them until lockMode is available in superdoc@latest.

Author: tupizz

apps/docs/snippets/extensions/structured-content.mdx

@@ -67,37 +67,6 @@ import { SuperDocEditor } from '/snippets/components/superdoc-editor.jsx'
         }
       },
     ],
-    [
-      {
-        label: 'Lock inline (sdtContentLocked)',
-        onClick: (superdoc) => {
-          const editor = superdoc?.activeEditor || superdoc?.editor
-          if (!editor?.commands) return
-          editor.commands.updateStructuredContentById('1', {
-            attrs: { lockMode: 'sdtContentLocked' },
-          });
-        }
-      },
-      {
-        label: 'Lock block (sdtContentLocked)',
-        onClick: (superdoc) => {
-          const editor = superdoc?.activeEditor || superdoc?.editor
-          if (!editor?.commands) return
-          editor.commands.updateStructuredContentById('2', {
-            attrs: { lockMode: 'sdtContentLocked' },
-          });
-        }
-      },
-      {
-        label: 'Unlock all',
-        onClick: (superdoc) => {
-          const editor = superdoc?.activeEditor || superdoc?.editor
-          if (!editor?.commands) return
-          editor.commands.updateStructuredContentById('1', { attrs: { lockMode: 'unlocked' } });
-          editor.commands.updateStructuredContentById('2', { attrs: { lockMode: 'unlocked' } });
-        }
-      },
-    ],
     [
       {
         label: 'Delete all fields',