removed pos-view article since it is deprecated (#13456)

erpnext/docs/user/manual/en/using-erpnext/articles/index.txt

@@ -8,5 +8,4 @@ bulk-rename
 renaming-documents
 search-filter
 tree-master-renaming
-pos-view
-letter-head-in-the-report
+letter-head-in-the-report

erpnext/docs/user/manual/en/using-erpnext/articles/pos-view.md

@@ -1,11 +0,0 @@
-#POS View
-
-POS (point of sale) view renders form in a different layout, optimized for the quick selection of items. This view has primarily been designed for the retail business.
-
-Using POS View, you can only create Sales Invoice, without switching to standard form view. For other transactions, like Sales Order, Delivery Note, Purchase Order, Purchase Receipt etc., POS View is only used for Item selection. For entering other values in the transaction, you should switch to form view.
-
-<img alt="POS View" class="screenshot" src="{{docs_base_url}}/assets/img/articles/pos-view.gif">
-
-For creating POS Invoice, check following help video.
-
-<iframe width="660" height="371" src="https://www.youtube.com/embed/4WkelWkbP_c" frameborder="0" allowfullscreen></iframe>