[FIX] hr_org_chart: Avoid write on employee just by loading the view

Before this commit:
When loading a employee form, a write is done due to hr_org_chart

After this commit:
No write should be performed

closes odoo/odoo#42214

Taskid: 2150314
X-original-commit: 6e150ee1
Signed-off-by: Yannick Tivisse (yti) <yti@odoo.com>