Right now, the quick create kanban card is having three buttons, Add, Edit
and Discard. In some languages, the translation terms of these buttons may be
quite long. This pushes the last button into second line and leads to an
ugly display.
This commit replaces the 'Discard' button with trash icon and makes sure that
all buttons are always in single line. If the strings are too long, they will
be cropped automatically.
Task ID-2373130
closesodoo/odoo#62326
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>