[REM] project:  remove onboarding mail
[REM] project:  remove onboarding mail

Removed current onboarding mail which was send when module was installed.
It is considered as not necessary now that we have a digest module sending
KPIs and tips by email.

This commit is related to task ID 30655 and PR #18318.

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