Revert "[fix] sale_project_advancement_ids is m2m"

This reverts commit e0825f54.

models/sale_project.py

@@ -46,7 +46,7 @@ class SaleProject(models.Model):
         tracking=2,
     )
     # TODO: to be checked, I get an error (TypeError: idsInRelation is undefined)
-    sale_project_advancement_ids = fields.Many2many(
+    sale_project_advancement_id = fields.Many2one(
         comodel_name="sale.project.advancement", string="Autre avancement", tracking=3
     )