The license is missing in most enterprise manifest so
the decision was taken to make it explicit in all cases.
When not defined, a warning will be triggered starting from
14.0 when falling back on the default LGPL-3.

closes odoo/odoo#74231

Related: odoo/enterprise#19850
Related: odoo/design-themes#43
Signed-off-by: Xavier Dollé (xdo) <xdo@odoo.com>