[FIX] sale: edit lead time

Allow the edition of Lead Time only when the SO is not confirmed yet
since the modification of the scheduled date on an existing picking is
not expected.

opw-2083070

closes odoo/odoo#38337

Signed-off-by: Nicolas Martinelli (nim) <nim@odoo.com>

addons/sale/views/sale_views.xml

@@ -525,7 +525,11 @@
                                         options='{"no_open": True}'
                                         optional="show"
                                     />
-                                    <field name="customer_lead" optional="hide"/>
+                                    <field
+                                        name="customer_lead"
+                                        optional="hide"
+                                        attrs="{'readonly': [('parent.state', 'not in', ['draft', 'sent'])]}"
+                                    />
                                     <field
                                         name="price_unit"
                                         attrs="{'readonly': [('qty_invoiced', '&gt;', 0)]}"