fix: batch selector for alternate item

[ankush]

1. Setup alternate items - A and B (both with batches)
2. Make A part of some BOM
3. Create work order and keep "allow alternative item" checked
4. create stock entry for stock transfer
5. save stock entry
6. Select alternate item
7. open row in stock entry and click on "pick batch no" to select batch no.
8. nothing shows up.

root cause: #25519 added pending qty section BUT the alternate item's info isn't present the global state from stock entry 🥲

erpnext/erpnext/public/js/utils/serial_no_batch_selector.js

Lines 542 to 549 in 1ee17b4

	function get_pending_qty_fields(me) {
	if (!check_can_calculate_pending_qty(me)) return [];
	const { frm: { doc: { fg_completed_qty }}, item: { item_code, stock_qty }} = me;
	const { qty_consumed_per_unit } = erpnext.stock.bom.items[item_code];
	const total_selected_qty = calc_total_selected_qty(me);
	const required_qty = flt(fg_completed_qty) * flt(qty_consumed_per_unit);
	const pending_qty = required_qty - (flt(stock_qty) + total_selected_qty);

Solution: disable pending qty computation for alternate items.

ref: ISS-21-22-10622