fix(sales): add sales user to read stock settings for js refresh code path

[blaggacao]

Context

erpnext/erpnext/selling/doctype/sales_order/sales_order.js

Lines 91 to 101 in e7f4b7b

	frappe.db.get_single_value("Stock Settings", "enable_stock_reservation").then((value) => {
	if (value) {
	frappe.db.get_single_value("Stock Settings", "auto_reserve_stock_for_sales_order").then((value) => {
	// If `Reserve Stock on Sales Order Submission` is enabled in Stock Settings, set Reserve Stock to 1 else 0.
	frm.set_value("reserve_stock", value ? 1 : 0);
	})
	} else {
	// If `Stock Reservation` is disabled in Stock Settings, set Reserve Stock to 0 and read only.
	frm.set_value("reserve_stock", 0);
	frm.set_df_property("reserve_stock", "read_only", 1);
	}

^^ This is a code path exercised by evey Sales User when e.g. creating a new sales order.

However the Sales User, alone, doesn't have access to Stock Settings.

This is clearly not working as intendet because there's no way a User with only Sale User role can actually, well, create a new Sale Order.

Every such time, the user is greated with a permission error message and the potentially important default setting on stock reservation is silently ignored as if it was disabled.

Proposed Solution

• Give Sale User role read-only access to Stock Settings.