It is not possible to hide charts added by administrators. However, you can configure permissions for viewing records/fields on a per user/department basis so that the records/fields for which a user does not have the view permission are not displayed in the aggregate result.

Only the records/fields for which the user has the view permission are subject to data aggregation.
If a field for which a user does not have the view permission is specified in the aggregation settings, the field is excluded from the data aggregation process and thus not displayed in the aggregate result.