[FIX] mrp: do not link BoM attachments to the Product

Steps to reproduce the issue:
- Create a storable product “P1” with two BoMs
- Open one of the BoMs and add an attachment
- Open the second BoM

Problem:
The attachment is added to all the BoMs.

opw-4263943

closes odoo#189016

Signed-off-by: William Henrotin (whe) <whe@odoo.com>

Author: DjamelTouati

addons/mrp/models/__init__.py

@@ -1,7 +1,6 @@
 # -*- coding: utf-8 -*-
 # Part of Odoo. See LICENSE file for full copyright and licensing details.
 
-from . import ir_attachment
 from . import product_document
 from . import res_config_settings
 from . import mrp_bom

addons/mrp/models/ir_attachment.py

@@ -170,7 +170,7 @@
                         </page>
                     </notebook>
                     </sheet>
-                    <chatter reload_on_attachment="True" open_attachments="True"/>
+                    <chatter/>
                 </form>
             </field>
         </record>