[FIX] hr_holidays: remove group by manager/validator

Since the renaming/split of model hr_holidays, the report does not
contain fields `manager_id` and `second_approver_id` anymore, hence
using the filters was crashing the client.

addons/hr_holidays/report/hr_leave_reports.xml

@@ -1,6 +1,6 @@
 <?xml version="1.0"?>
 <odoo>
-    
+
     <record id="view_hr_holidays_filter_report" model="ir.ui.view">
         <field name="name">hr.holidays.filter</field>
         <field name="model">hr.leave.report</field>
@@ -33,8 +33,6 @@
                     <filter name="group_name" string="Description" context="{'group_by':'name'}"/>
                     <filter name="group_employee" string="Employee" context="{'group_by':'employee_id'}"/>
                     <filter name="group_category" string="Category" context="{'group_by':'category_id'}"/>
-                    <filter name="group_manager" string="Manager" context="{'group_by':'manager_id'}"/>
-                    <filter name="group_second_approver_id" string="Validator" context="{'group_by':'second_approver_id'}"/>
                     <filter name="group_type" string="Type" context="{'group_by':'holiday_status_id'}"/>
                     <separator/>
                     <filter name="group_date_from" string="Start Month" context="{'group_by':'date_from'}"/>