docs : update dead link on main-menu page (#8454)

dev-docs/docs/@excalidraw/excalidraw/api/children-components/main-menu.mdx

@@ -133,7 +133,7 @@ function App() {
 }
 ```
 
-Here is a [complete list](https://github.com/excalidraw/excalidraw/blob/master/packages/excalidraw/components/mainMenu/DefaultItems.tsx) of the default items.
+Here is a [complete list](https://github.com/excalidraw/excalidraw/blob/master/packages/excalidraw/components/main-menu/DefaultItems.tsx) of the default items.
 
 ### MainMenu.Group