[FIX] website: restore narrow mega menu

Since [1], the narrow mega menu is broken because with BS5 the class
'dropdown-menu' is having a more specific CSS rule to set its left
property. This commit increases the specificity of Odoo related rule.

[1]: https://github.com/odoo/odoo/commit/c48f57ea2538ad51e00ac27d58f8e191781444f3

Closes https://github.com/odoo/odoo/pull/107074

closes odoo/odoo#107177

X-original-commit: 27e66ae4c9ccfbc3f309cac9729fe097226e0cae
Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>

addons/website/static/src/scss/website.scss

@@ -1187,7 +1187,7 @@ header {
     }
 }
 
-.o_mega_menu_container_size {
+.dropdown-menu.o_mega_menu_container_size {
     $-header-template: o-website-value('header-template');
     @if not index(('sidebar', 'hamburger', 'magazine'), $-header-template) {
         $bp: if($-header-template == 'minimalist', md, lg);