fix: update_nsm only in warehouse creation (#54165)

(cherry picked from commit b0e3fa3)

Author: nishkagosalia

erpnext/stock/doctype/warehouse/warehouse.py

@@ -65,7 +65,8 @@ def validate(self):
 		self.warn_about_multiple_warehouse_account()
 
 	def on_update(self):
-		self.update_nsm_model()
+		if self.is_new() or self.has_value_changed("parent_warehouse"):
+			self.update_nsm_model()
 
 	def update_nsm_model(self):
 		frappe.utils.nestedset.update_nsm(self)