[FIX] project: task manager

Following commit 1dbccc8, there is no `user_id` field on the analytic
account anymore. However, a field `user_id` was added directly on the
project with commit 908f416.

opw-672333

addons/project/project.py

@@ -456,7 +456,7 @@ class task(osv.osv):
         'remaining_hours': fields.float('Remaining Hours', digits=(16,2), help="Total remaining time, can be re-estimated periodically by the assignee of the task."),
         'user_id': fields.many2one('res.users', 'Assigned to', select=True, track_visibility='onchange'),
         'partner_id': fields.many2one('res.partner', 'Customer'),
-        'manager_id': fields.related('project_id', 'analytic_account_id', 'user_id', type='many2one', relation='res.users', string='Project Manager'),
+        'manager_id': fields.related('project_id', 'user_id', type='many2one', relation='res.users', string='Project Manager'),
         'company_id': fields.many2one('res.company', 'Company'),
         'id': fields.integer('ID', readonly=True),
         'color': fields.integer('Color Index'),