Bug
===
Since 569d35bc a fix have been provided
to fix the vertical position of the emoji widget in mobile view.

But the fix have been done in a wrong way and we should use the Odoo CSS
class instead to detect mobile (and not a bootstrap media query).

Task 2253851

closes odoo/odoo#64689

Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>