[FIX] website: fix overflowing navbar links on mobile

This commit fixes a bug with the navbar links in the header of a website
on mobile. When the text of a link is long enough to be wider than the
screen, the text does not wrap to the next line as intended, but instead
overflows to the right outside of the screen, causing part of the text
to be hidden.

Steps to reproduce the bug:

- Edit the text of one of the menu links on a website to make it longer
than the width of the mobile screen.
- Bug: In mobile view, part of the link text is hidden.

This bug occurs with both the "default" hamburger type and the
"off-canvas" hamburger type.

opw-3233684

closes odoo/odoo#119998

Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>