[REF] stock,mrp: remove index of priority fields

Indexed of boolean values is quite useless and the one of `priority`
(MO/Pickings) can be only used in filter search view (`starred`).
Then remove priority indexes from `stock_move`, `stock_picking` and
`mrp_production`.

task-2389380

addons/mrp/models/mrp_production.py

@@ -74,7 +74,7 @@ class MrpProduction(models.Model):
     name = fields.Char(
         'Reference', copy=False, readonly=True, default=lambda x: _('New'))
     priority = fields.Selection(
-        PROCUREMENT_PRIORITIES, string='Priority', default='0', index=True,
+        PROCUREMENT_PRIORITIES, string='Priority', default='0',
         help="Components will be reserved first for the MO with the highest priorities.")
     backorder_sequence = fields.Integer("Backorder Sequence", default=0, copy=False, help="Backorder sequence, if equals to 0 means there is not related backorder")
     origin = fields.Char(

addons/stock/models/stock_move.py

@@ -32,7 +32,7 @@ class StockMove(models.Model):
     sequence = fields.Integer('Sequence', default=10)
     priority = fields.Selection(
         PROCUREMENT_PRIORITIES, 'Priority', default='0',
-        compute="_compute_priority", store=True, index=True)
+        compute="_compute_priority", store=True)
     date = fields.Datetime(
         'Date Scheduled', default=fields.Datetime.now, index=True, required=True,
         help="Scheduled date until move is done, then date of actual move processing")

addons/stock/models/stock_picking.py

@@ -279,7 +279,7 @@ class Picking(models.Model):
         'procurement.group', 'Procurement Group',
         readonly=True, related='move_lines.group_id', store=True)
     priority = fields.Selection(
-        PROCUREMENT_PRIORITIES, string='Priority', default='0', index=True,
+        PROCUREMENT_PRIORITIES, string='Priority', default='0',
         help="Products will be reserved first for the transfers with the highest priorities.")
     scheduled_date = fields.Datetime(
         'Scheduled Date', compute='_compute_scheduled_date', inverse='_set_scheduled_date', store=True,