[FIX]hr_holidays: leave request traceback in arabic

Step to reproduce:
- Switch language to arabic
- Go to Time off
- Click on 'New TIme Off'

Current behaviour:
- Traceback
Default date_from and date_to are given in arabic which cannot be parsed by the field

Behaviour after PR:
- Default date_from and date_to are given in english and then translated via the field

opw-2755258

closes odoo/odoo#84902

Signed-off-by: Kevin Baptiste <kba@odoo.com>