[FIX] project: local variable task referenced in write

When a user creates the task without a name field and directly clicks on the
'Mark as Done' button, will give UnboundLocalError like the local variable
'task' referenced before assignment.

Steps to produce:
- Install the 'Field Service' module.
- Field Service > My Tasks > Open any task.
- Make the name field unrequired (Studio or Edit form View)
- Create a new task > Set the Customer field and leave the Name field as blank.
- Before saving the task click on the 'Mark as Done' button > Discard Changes.
- Error will be produced.

Fixing the indentation for `task.date_last_stage_update = now` will solve this
issue. We have used the task variable in for loop.

Sentry-4276832131

closes odoo/odoo#126752

X-original-commit: c3649a32c98d7093610a4367b1e72c1b4b0085b7
Signed-off-by: Xavier Bol (xbo) <xbo@odoo.com>

addons/project/models/project_task.py

@@ -1087,8 +1087,8 @@ class Task(models.Model):
                 if task.allow_task_dependencies:
                     if task.is_blocked_by_dependences() and vals['state'] not in CLOSED_STATES and vals['state'] != '04_waiting_normal':
                         task.state = '04_waiting_normal'
-            if vals['state'] in CLOSED_STATES:
-                task.date_last_stage_update = now
+                if vals['state'] in CLOSED_STATES:
+                    task.date_last_stage_update = now
 
         self._task_message_auto_subscribe_notify({task: task.user_ids - old_user_ids[task] - self.env.user for task in self})
         return result