Remove Test Letter Head from GSTR-1 (#15591)

diff --git a/erpnext/regional/report/gstr_1/gstr_1.json b/erpnext/regional/report/gstr_1/gstr_1.json
index a71d89e..4ef8d53 100644
--- a/erpnext/regional/report/gstr_1/gstr_1.json
+++ b/erpnext/regional/report/gstr_1/gstr_1.json
@@ -7,7 +7,6 @@
  "doctype": "Report", 
  "idx": 0, 
  "is_standard": "Yes", 
- "letter_head": "test", 
  "modified": "2018-01-02 17:56:15.379347", 
  "modified_by": "Administrator", 
  "module": "Regional", 
@@ -27,4 +26,4 @@
    "role": "Auditor"
   }
  ]
-}
\ No newline at end of file
+}