create a recursion
Problem
---------
When you have an analytics plans which is the parent of another one, you
should not be able to choose the child plan as parent of this one.
A user has the possibility to do it; when he saves, we he gets the
error: Recursion Detected.
Objective
---------
Don't show the child plans of an analytics plan to avoid the user to
choose something that raises the error.
Solution
---------
Update the domain of the field `parent_id` to exclude the analytic plans
that are the children of the current plan.
task-3414188
closesodoo/odoo#128302
Signed-off-by: Quentin De Paoli <qdp@odoo.com>