[FIX] sale_timesheet: currency displayed in project mapping

This commit's purpose is to display the correct currency for the hourly
cost of employee in the project sol mapping.
Currently, the currency displayed is the one of the sol instead of the
currency of the employee. This is due to this commit:83760b9
We added a monetary widget, but we are feeding it the wrong id.

After this commit, the correct currency is displayed

closes #159567

X-original-commit: 8603d62
Signed-off-by: Xavier Bol (xbo) <xbo@odoo.com>

addons/sale_timesheet/views/project_task_views.xml

@@ -20,7 +20,7 @@
                             <field name="employee_id" options="{'no_create': True}" widget="many2one_avatar_user"/>
                             <field name="sale_line_id" attrs="{'required': True}" options="{'no_create': True}" context="{'search_default_order_id': sale_order_id}"/>
                             <field name="price_unit" widget="monetary" force_save="1" options="{'currency_field': 'currency_id'}"/>
-                            <field name="display_cost" widget="monetary" options="{'currency_field': 'currency_id'}"/>
+                            <field name="display_cost" widget="monetary" options="{'currency_field': 'cost_currency_id'}"/>
                             <field name="is_cost_changed" invisible="1"/>
                             <field name="currency_id" invisible="1"/>
                             <field name="cost_currency_id" invisible="1"/>