[FIX] account: open Monthly Turnover partner in graph mode

Tree view gives no information
Fixes #4195

addons/account/report/account_invoice_report_view.xml

@@ -103,7 +103,8 @@
         groups="group_account_manager"
         context="{'search_default_partner_id':[active_id], 'search_default_month':1,'search_default_user':1,'group_by_no_leaf':1,'group_by':[]}"
         res_model="account.invoice.report"
-        src_model="res.partner"/>
+        src_model="res.partner"
+        view_mode="graph"/>
 
 </data>
 </openerp>