Update customs_tariff_number.json

Main information of tariff numbers are the number. A description is more or less double information as this is mostly the number. Thus a description should not be mandetory.
diff --git a/erpnext/stock/doctype/customs_tariff_number/customs_tariff_number.json b/erpnext/stock/doctype/customs_tariff_number/customs_tariff_number.json
index 07992b8..90385a2 100644
--- a/erpnext/stock/doctype/customs_tariff_number/customs_tariff_number.json
+++ b/erpnext/stock/doctype/customs_tariff_number/customs_tariff_number.json
@@ -71,7 +71,7 @@
    "read_only": 0, 
    "remember_last_selected_value": 0, 
    "report_hide": 0, 
-   "reqd": 1, 
+   "reqd": 0, 
    "search_index": 0, 
    "set_only_once": 0, 
    "translatable": 0, 
@@ -143,4 +143,4 @@
  "track_changes": 1, 
  "track_seen": 0, 
  "track_views": 0
-}
\ No newline at end of file
+}