Purpose: make `name` a non-required field in form view
Currently `name` field in the mass mailing is visible only in the debug
mode, and is set via create method based on `subject`. If user tries to
create a new mass mailing object in non debug mode, it gives a warning.
This commit fixes the behavior by setting `name` field as non-required
in the form-view and thus avoiding the warning when field is not visible.
It will not cause issue since the `name` field is coming from the model
`utm.source` and is already a required through field definition.
Task 2178214
PR #43709
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>