[IMP] test_mail: clean reminder-related activity tests
[IMP] test_mail: clean reminder-related activity tests

It has not been done completely at f488dc58c37fdc7fd49df759165de641e213444b.

ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo