Context:
During the refactor 68fbdc9640,
expense rights were improved but two cases were forgotten.
Before this commit:
1. sudo would not work as the rights were checking the groups
2. system admins were considered as being expense admins too, which may
not be the case if the system admin user changes
and the correct group `group_hr_expense_manager` is not given.
System admins should always be able to edit expenses
when it make sense.
After this commit:
Sudoed and group_system users are considered as expense admins
closesodoo/odoo#158583
Signed-off-by: Julien Van Roy (juvr) <juvr@odoo.com>