[FIX] web: no duplication function for `change_menu_section`
[FIX] web: no duplication function for `change_menu_section`

Revision on https://github.com/odoo/odoo/commit/b7cf456560dc4fd7c1217ba90f0b5609466ede50

The commit above assumed the function `change_menu_section` was
mistakenly removed. However, it was turned into a handler function
and renamed according to our JS guidelines `_onChangeMenuSection`.

This commit removes the duplicated logic by removing the
function `_onChangeMenuSection` and using `change_menu_section`
as the handler for the bus event `change_menu_section`.

closes odoo/odoo#27809
ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo