[FIX] stock: forecast button color

adress both use cases in :
https://github.com/odoo/odoo/commit/ed2849a55c1463689cbc201a782b0200207bfd37
and
https://github.com/odoo/odoo/commit/4248aac2d224363a6ac4a59881bdb7c321623e4b



button should be red if there's no qty in stock but still be green if
the qty was reserved for the move

closes odoo/odoo#135881

X-original-commit: e243ba49137c5a6151c6da74ef4ed253f81754d9
Signed-off-by: William Henrotin (whe) <whe@odoo.com>
Signed-off-by: Walid Hanniche (waha) <waha@odoo.com>