Fix for task 2620026.

_get_bom_component_qty function is only referred to once in the whole odoo app,
which is on addons/sale_mrp/models/account_move.py#22.

The result returned from this function is used as a multiplier to quantity
to convert into the expected UoM. However, the quantity being referred to on
_stock_account_get_anglo_saxon_price_unit (qty_invoiced, qty_to_invoice), are
already converted into the SO Line's product's default UoM. In this function,
it however tries to convert 1 from SO Line's UoM to BoM's UOM.

With this, if Product UoM=x, SO Line UoM=y, BOM UoM=x, in the function _stock_account_get_anglo_saxon_price_unit,
the quantities will be multiplied by the same factor twice, resulting to the incorrect computation of price_unit to follow.

Part-of: odoo/odoo#81355