Minor nav-menu hook docs fix

[tyxla]

In the documentation of the wp_update_nav_menu_item hook (in wp-includes/nav-menu.php), the @see block is:

* @see wp_update_nav_menu_items()

while it should be:

* @see wp_update_nav_menu_item()

This typo seems to have been introduced in #27367.

[tyxla]

Not sure if this is worth a patch, but attaching anyway.

[tyxla]

Fix a typo in the @see block of the wp_update_nav_menu_item hook documentation.

[SergeyBiryukov]

In 31521:

Fix a typo in wp_update_nav_menu_item hook documentation.

props tyxla.
fixes #31338.