[FIX] mrp: MO planned when all WO are planned

This pr fixes a bug where a validation error occurs in the timesheet
wizard.
Indeed, when the user enter manually a start or end date in a workorder,
the whole MO becomes "plan".
The problem here was that if the user opens the wizard of another
workorder (on the same MO) that has no start/ end date set, and then if
he saves (no matter if he changed something), it will trigger a
validation error because the start and end date of the workorder is
required in that view if the MO is planned.

closes odoo/odoo#120386

X-original-commit: c9728858aa46e6cb1a3d39cbc8da8e175007e456
Signed-off-by: Arnold Moyaux (arm) <arm@odoo.com>

addons/mrp/views/mrp_workorder_views.xml

@@ -159,9 +159,9 @@
                         <label for="date_start" string="Start Date" attrs="{'invisible': [('state', 'not in', ['progress', 'done', 'cancel'])]}"/>
                         <div class="oe_inline">
                             <field name="is_planned" invisible="1"/>
-                            <field name="date_start" class="mr8 oe_inline" attrs="{'required': [('is_planned', '=', True)]}"/>
+                            <field name="date_start" class="mr8 oe_inline"/>
                             <strong class="mr8 oe_inline">to</strong>
-                            <field name="date_finished" class="oe_inline" attrs="{'required': [('is_planned', '=', True)]}"/>
+                            <field name="date_finished" class="oe_inline"/>
                             <field name="show_json_popover" invisible="1"/>
                             <field name="json_popover" widget="mrp_workorder_popover" class="oe_inline mx-2" attrs="{'invisible': [('show_json_popover', '=', False)]}"/>
                         </div>