slapos_erp5: accounting period are only readable/writable by accountant

master/bt5/slapos_erp5/PortalTypeRolesTemplateItem/Accounting%20Period.xml

 <type_roles>
   <role id='Assignor'>
-   <property id='title'>Company group</property>
-   <multi_property id='categories'>local_role_group/group</multi_property>
-   <multi_property id='category'>group/company</multi_property>
-   <multi_property id='base_category'>group</multi_property>
+   <property id='title'>Writable for Accountant</property>
+   <multi_property id='categories'>local_role_group/function</multi_property>
+   <multi_property id='category'>function/accounting</multi_property>
+   <multi_property id='base_category'>function</multi_property>
   </role>
 </type_roles>
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