[FIX] project: remove stage group by in all tasks list view

This commit removes the default `stage_id` group in the
'All Tasks' list view, as it is causing performance issues

closes odoo/odoo#113435

X-original-commit: 759d7b1a30841535de57c19954eff3507dd61eff
Signed-off-by: Xavier Bol (xbo) <xbo@odoo.com>
Signed-off-by: Larcin Vincent (vila) <vila@odoo.com>

addons/project/views/project_views.xml

@@ -1711,7 +1711,7 @@
             <field name="mode">primary</field>
             <field name="arch" type="xml">
                 <tree position="attributes">
-                    <attribute name="default_group_by">project_id</attribute>
+                    <attribute name="default_group_by"/>
                 </tree>
                 <field name="project_id" position="attributes">
                     <attribute name="invisible">0</attribute>