Update serial_no.json

change "delivery_document_type" to Link and ""delivery_document_no" to Dynamic link will be more convenient, like "purchase_document_type" and "purchase_document_no".
diff --git a/erpnext/stock/doctype/serial_no/serial_no.json b/erpnext/stock/doctype/serial_no/serial_no.json
index c177325..18005b6 100644
--- a/erpnext/stock/doctype/serial_no/serial_no.json
+++ b/erpnext/stock/doctype/serial_no/serial_no.json
@@ -504,7 +504,7 @@
    "bold": 0, 
    "collapsible": 0, 
    "fieldname": "delivery_document_type", 
-   "fieldtype": "Select", 
+   "fieldtype": "Link", 
    "hidden": 0, 
    "ignore_user_permissions": 0, 
    "in_filter": 1, 
@@ -512,7 +512,7 @@
    "label": "Delivery Document Type", 
    "length": 0, 
    "no_copy": 1, 
-   "options": "\nDelivery Note\nSales Invoice\nStock Entry\nPurchase Receipt", 
+   "options": "DocType", 
    "permlevel": 0, 
    "print_hide": 0, 
    "read_only": 1, 
@@ -527,7 +527,7 @@
    "bold": 0, 
    "collapsible": 0, 
    "fieldname": "delivery_document_no", 
-   "fieldtype": "Data", 
+   "fieldtype": "Dynamic Link", 
    "hidden": 0, 
    "ignore_user_permissions": 0, 
    "in_filter": 1, 
@@ -535,6 +535,7 @@
    "label": "Delivery Document No", 
    "length": 0, 
    "no_copy": 1, 
+   "options": "delivery_document_type"
    "permlevel": 0, 
    "print_hide": 0, 
    "read_only": 1, 
@@ -1003,4 +1004,4 @@
  "search_fields": "item_code", 
  "sort_field": "modified", 
  "sort_order": "DESC"
-}
\ No newline at end of file
+}