fix: Do no apply pricing rule on qty change for mapped docs

(cherry picked from commit 2b1242170c)

erpnext/public/js/controllers/transaction.js

@@ -1246,8 +1246,8 @@ erpnext.TransactionController = class TransactionController extends erpnext.taxe
 	}
 
 	qty(doc, cdt, cdn) {
-		if (!this.frm.doc.__onload?.load_after_mapping) {
-			let item = frappe.get_doc(cdt, cdn);
+		let item = frappe.get_doc(cdt, cdn);
+		if (!this.is_a_mapped_document(item)) {
 			// item.pricing_rules = ''
 			frappe.run_serially([
 				() => this.remove_pricing_rule_for_item(item),