[FIX] project: remove default group by user

This commit removes the default group by User for the Tasks Analysis
report, which was active once one clicked on "Open Tasks" in the Project
Update Kanban view.

This commit also removes the default group by user in the graph view
(which is induced by the field in the graph arch, through graph view
init function).

Issue :
The graph view of report.project.task.user is not able to render the
project_id>user_id groupby since the number of rows to display is to
high.

After considering improvements client-side (e.g. drop last groupby
when there are too many datasets to render), we concluded that the case
of report.project.task.user is rather isolated. The real issue is that
this 'complex' two-level groupby is forced in the view itself, making
it unusable on larger databases (e.g. next.odoo.com).

On top of that, project_id and user_id are usually dependent dimensions
(users are usually working in the same few projects).

PR: #73299

task-2588087

closes odoo/odoo#77013

X-original-commit: 605b4e109afabaff0876ca92cecfce9a6c615977
Signed-off-by: LTU-Odoo <IT-Ideas@users.noreply.github.com>

addons/project/models/project.py

@@ -681,7 +681,6 @@ class Project(models.Model):
                     'active_id': self.id,
                     'search_default_open_tasks': True,
                     'search_default_Stage': True,
-                    'search_default_User': True
                 }),
             },
             'value': counts['open_tasks_count']

addons/project/report/project_report_views.xml

@@ -17,7 +17,8 @@
             <field name="arch" type="xml">
                 <graph string="Tasks Analysis" sample="1">
                      <field name="project_id"/>
-                     <field name="user_ids"/>
+                     <field name="stage_id"/>
+                     <field name="user_ids" invisible="1"/>
                      <field name="nbr" invisible="1"/>
                  </graph>
              </field>