perf: don't track seen for POS Invoice (#46187)

This is a moving doctype. Do people even browse the list view? 

It doesn't make much sense, either. POS INvoices are rarely "reviewed" by multiple users.

erpnext/accounts/doctype/pos_invoice/pos_invoice.json

@@ -1625,6 +1625,5 @@
  "states": [],
  "timeline_field": "customer",
  "title_field": "customer_name",
- "track_changes": 1,
+ "track_changes": 1
- "track_seen": 1
+}
-}