[FIX] account: Link between analytic line and move line

Steps to reproduce the bug:

- Create an analytic account AA
- Create a journal entry with a debit(L1) and a credit(L2)
- Set an analytic account on L1
- Validate the journal entry and an account analytic line AAL has benn created
- Go on the journal item  L1 by the menu Journal Items
- Remove the analytic account of L1

Bug:

The account analytic of AAL was still AA

The AA of a journal item cannot be changed when the entry is posted.

opw:2158057

closes odoo/odoo#43214

Signed-off-by: Simon Goffin (sig) <sig@openerp.com>

addons/account/views/account_view.xml

@@ -1283,7 +1283,7 @@
                                         <field name="blocked"/>
                                     </group>
                                     <group string="Analytic" groups="analytic.group_analytic_accounting,analytic.group_analytic_tags">
-                                        <field name="analytic_account_id" groups="analytic.group_analytic_accounting"/>
+                                        <field name="analytic_account_id" groups="analytic.group_analytic_accounting" attrs="{'readonly':[('parent_state','=','posted')]}"/>
                                         <field name="analytic_tag_ids" groups="analytic.group_analytic_tags" widget="many2many_tags"/>
                                     </group>
                                 </group>