Remove unused class parameter in the function to find move for stock lot

The function is called only when the state as parameter.

Closes #14963
(grafted from 3cb38ab5ba4a2321cab4bf5f2954e4842a1c733d)

--HG--
branch : 8.0

modules/stock_lot/stock.py

@@ -126,7 +126,7 @@ class Lot(DeactivableMixin, ModelSQL, ModelView, LotMixin, StockMixin):
         pool = Pool()
         Move = pool.get('stock.move')
 
-        def find_moves(cls, state=None):
+        def find_moves(state=None):
             domain = [
                 ('lot', 'in', lots)
                 ]